need infos please

I gave infos:
KMail encountered a fatal error and will terminate now.
The error was:
Failed to fetch the resource collection.

it doesn't give me info to fix it...
Which collection ?
migration from kmail1 ?
etc.

What do you mean by collection or migration? This happens when I open up kmail.

Created attachment 65884 [details]
Kmail log

I've recently encountered this problem on Arch Linux.

KDE version: 4.7.3

I'll be happy to provide any other useful information.

After upgrading to 4.8.2, crash at startup :
kmail
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbehave.
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbehave.
Known subscriber "kmail2" subscribes again 
Known subscriber "kmail2" subscribes again 
"/usr/bin/kmail(6699)" Soprano: "org.freedesktop.DBus.Error.ServiceUnknown - The name org.kde.nepomuk.services.nepomukstorage was not provided by any .service files"
"/usr/bin/kmail(6699)" Soprano: "QLocalSocket::connectToServer: Invalid name"
"/usr/bin/kmail(6699)" Soprano: "org.freedesktop.DBus.Error.ServiceUnknown - The name org.kde.nepomuk.services.nepomukstorage was not provided by any .service files"
"/usr/bin/kmail(6699)" Soprano: "QLocalSocket::connectToServer: Invalid name"
"/usr/bin/kmail(6699)" Soprano: "org.freedesktop.DBus.Error.ServiceUnknown - The name org.kde.nepomuk.services.nepomukstorage was not provided by any .service files"
"/usr/bin/kmail(6699)" Soprano: "QLocalSocket::connectToServer: Invalid name"
"/usr/bin/kmail(6699)" Soprano: "org.freedesktop.DBus.Error.ServiceUnknown - The name org.kde.nepomuk.services.nepomukstorage was not provided by any .service files"
"/usr/bin/kmail(6699)" Soprano: "Unsupported operation (2)": "Invalid model"
"/usr/bin/kmail(6699)" Soprano: "org.freedesktop.DBus.Error.ServiceUnknown - The name org.kde.nepomuk.services.nepomukstorage was not provided by any .service files"
"/usr/bin/kmail(6699)" Soprano: "Unsupported operation (2)": "Invalid model"
"/usr/bin/kmail(6699)" Soprano: "Invalid iterator."
"/usr/bin/kmail(6699)" Soprano: "org.freedesktop.DBus.Error.ServiceUnknown - The name org.kde.nepomuk.services.nepomukstorage was not provided by any .service files"
"/usr/bin/kmail(6699)" Soprano: "QLocalSocket::connectToServer: Invalid name"
Known subscriber "kmail2" subscribes again 
Known subscriber "kmail2" subscribes again 
kmail2(6699)/kdepimlibs (mailtransport): Could not access Outbox. 
delafond@delafond-desktop:~$ "/usr/bin/kmail(6699)" Soprano: "org.freedesktop.DBus.Error.ServiceUnknown - The name org.kde.nepomuk.services.nepomukstorage was not provided by any .service files"
"/usr/bin/kmail(6699)" Soprano: "QLocalSocket::connectToServer: Invalid name"
"/usr/bin/kmail(6699)" Soprano: "org.freedesktop.DBus.Error.ServiceUnknown - The name org.kde.nepomuk.services.nepomukstorage was not provided by any .service files"
"/usr/bin/kmail(6699)" Soprano: "Unsupported operation (2)": "Invalid model"
"/usr/bin/kmail(6699)" Soprano: "org.freedesktop.DBus.Error.ServiceUnknown - The name org.kde.nepomuk.services.nepomukstorage was not provided by any .service files"
"/usr/bin/kmail(6699)" Soprano: "Unsupported operation (2)": "Invalid model"
"/usr/bin/kmail(6699)" Soprano: "Invalid iterator."
Database "akonadi" opened using driver "QMYSQL" 
Database "akonadi" opened using driver "QMYSQL" 
kmail2(6699)/libakonadi Akonadi::SpecialCollectionsRequestJob::slotResult: Failed SpecialCollectionsRequestJob::slotResult "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
kmail2(6699) MailCommon::Kernel::emergencyExit: "KMail a rencontré une erreur fatale et va s'arrêter maintenant.
L'erreur est :
Échec de la récupération de la collection de la ressource." 
kmail2(6699)/libakonadi Akonadi::SpecialCollectionsRequestJob::slotResult: Failed SpecialCollectionsRequestJob::slotResult "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
kmail2(6699) MailCommon::Kernel::emergencyExit: "KMail a rencontré une erreur fatale et va s'arrêter maintenant.
L'erreur est :
Échec de la récupération de la collection de la ressource." 
kmail2(6699)/libakonadi Akonadi::SpecialCollectionsRequestJobPrivate::resourceScanResult: Failed to request resource "akonadi_mixedmaildir_resource_0" : "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
kmail2(6699)/libakonadi Akonadi::SpecialCollectionsRequestJob::slotResult: Failed SpecialCollectionsRequestJob::slotResult "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
kmail2(6699) MailCommon::Kernel::emergencyExit: "KMail a rencontré une erreur fatale et va s'arrêter maintenant.
L'erreur est :
Échec de la récupération de la collection de la ressource." 
kmail2(6699)/libakonadi Akonadi::SpecialCollectionsRequestJobPrivate::resourceScanResult: Failed to request resource "akonadi_mixedmaildir_resource_0" : "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
kmail2(6699)/libakonadi Akonadi::SpecialCollectionsRequestJob::slotResult: Failed SpecialCollectionsRequestJob::slotResult "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
kmail2(6699) MailCommon::Kernel::emergencyExit: "KMail a rencontré une erreur fatale et va s'arrêter maintenant.
L'erreur est :
Échec de la récupération de la collection de la ressource." 
kmail2(6699)/libakonadi Akonadi::SpecialCollectionsRequestJobPrivate::resourceScanResult: Failed to request resource "akonadi_mixedmaildir_resource_0" : "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
Setting new source 
New source:  QUrl( "file:///usr/share/sounds/KDE-Sys-App-Error-Critical.ogg" )  
kmail2(6699)/libakonadi Akonadi::SpecialCollectionsRequestJob::slotResult: Failed SpecialCollectionsRequestJob::slotResult "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
kmail2(6699) MailCommon::Kernel::emergencyExit: "KMail a rencontré une erreur fatale et va s'arrêter maintenant.
L'erreur est :
Échec de la récupération de la collection de la ressource." 
kmail2(6699)/libakonadi Akonadi::SpecialCollectionsRequestJobPrivate::resourceScanResult: Failed to request resource "akonadi_mixedmaildir_resource_0" : "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
kmail2(6699)/libakonadi Akonadi::SpecialCollectionsRequestJob::slotResult: Failed SpecialCollectionsRequestJob::slotResult "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
kmail2(6699) MailCommon::Kernel::emergencyExit: "KMail a rencontré une erreur fatale et va s'arrêter maintenant.
L'erreur est :
Échec de la récupération de la collection de la ressource." 
kmail2(6699)/libakonadi Akonadi::SpecialCollectionsRequestJobPrivate::resourceScanResult: Failed to request resource "akonadi_mixedmaildir_resource_0" : "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
Transitioning to state "playing" 
About to finish 
Got next source. Waiting for end of current. 
State change 
New source:  QUrl( "" )  
Moving from "ready" 1 to "paused" 4 
Stream changed to file:///usr/share/sounds/KDE-Sys-App-Error-Critical.ogg 
Finally got a source 
About to finish 
Got next source. Waiting for end of current. 
New source:  QUrl( "" )  
Finally got a source 
State change 
Moving from "paused" 4 to "playing" 2 
Transitioning to state "ready" 
State change 
Moving from "playing" 2 to "paused" 4 
State change 
Moving from "paused" 4 to "ready" 1 
void Akonadi::NotificationSource::serviceUnregistered(const QString&) Notification source "kmail2" now serving: () 
void Akonadi::NotificationSource::unsubscribe() "kmail2" 
akonadi_pop3_resource_8(5997)/libakonadi Akonadi::SpecialCollectionsRequestJob::slotResult: Failed SpecialCollectionsRequestJob::slotResult "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
akonadi_pop3_resource_8(5997)/akonadiresource (pop3) POP3Resource::cancelSync: ============== ERROR DURING POP3 SYNC ========================== 
akonadi_pop3_resource_8(5997)/akonadiresource (pop3) POP3Resource::cancelSync: "Erreur en essayant de retrouver le dossier local de boîte de réception. Abandon de la vérification du courrier.
Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
akonadi_pop3_resource_8(5997)/akonadiresource (pop3) POP3Resource::saveSeenUIDList: UID list from server is not valid. 
akonadi_pop3_resource_8(5997)/libakonadi Akonadi::SpecialCollectionsRequestJobPrivate::resourceScanResult: Failed to request resource "akonadi_mixedmaildir_resource_0" : "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
akonadi_pop3_resource_8(5997)/libakonadi Akonadi::SpecialCollectionsRequestJob::slotResult: Failed SpecialCollectionsRequestJob::slotResult "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
akonadi_pop3_resource_8(5997)/akonadiresource (pop3) POP3Resource::cancelSync: ============== ERROR DURING POP3 SYNC ========================== 
akonadi_pop3_resource_8(5997)/akonadiresource (pop3) POP3Resource::cancelSync: "Erreur en essayant de retrouver le dossier local de boîte de réception. Abandon de la vérification du courrier.
Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 
akonadi_pop3_resource_8(5997)/akonadiresource (pop3) POP3Resource::saveSeenUIDList: UID list from server is not valid. 
akonadi_pop3_resource_8(5997)/libakonadi Akonadi::SpecialCollectionsRequestJobPrivate::resourceScanResult: Failed to request resource "akonadi_mixedmaildir_resource_0" : "Erreur inconnue. (Échec de la récupération de la collection de la ressource.)" 

KMail used to be usable in 4.8.1, except it crashed every 5 or 10 clicks.
Even worse in 4.8.2 : impossible to launch.

$ akonadictl start
Akonadi is already running. 

ProcessControl: Application '/usr/bin/akonadi_pop3_resource' stopped unexpectedly (Process crashed)
Application '/usr/bin/akonadi_pop3_resource' crashed. No restart!

This bug is now fixed. Look at release KDE 4.9 and https://bugs.kde.org/show_bug.cgi?id=124111