Version:           4.8 (using Devel) 
OS:                Linux

after resuming from hibernation I got the following message from Kalarm:
   Failed to update alarm.
   (Unknown error. (NO Unable to retrieve items ))

I then restarted Kalarm and the app's window was blank, no alarms shown but the calendar file was full

Starting Kalarm again from Konsole gave:
kalarm
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbehave.
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbehave.

Restarting KDE resolved the problem

It was suggested to me that the problem was that the Akonadi
server may not always resume properly when waking from hibernation

note: as Kalarm is the only Akonadi related app I use I can not state if other apps (Kmail, Kaggregator) acted similarly 

Reproducible: Didn't try

Steps to Reproduce:
hibernate KDE

Actual Results:  
Kalarm did not show any alarms

Expected Results:  
Kalarm works as it has always