Version:           unknown (using KDE 3.5.7, Debian Package 4:3.5.7.dfsg.1-5 (lenny/sid))
Compiler:          Target: i486-linux-gnu
OS:                Linux (i686) release 2.6.21-2-686

while issuing a kbuildsycoca command i get warnings that seams irrelevant since the .desktop files (in most cases) are in place.
both globally (/usr/share/mimelnk) and per user/locally (/home/usr/.kde/share/mimelnk).

for example: mime application/ogg is in /usr/share/mimelnk/application and in /home/foo/.kde/share/mimelnk/application
and i got a warning for it:
kbuildsycoca: WARNING: '/usr/share/applications/mplayer.desktop' specifies undefined mimetype/servicetype 'application/ogg'

here is : /usr/share/applications/mplayer.desktop
[Desktop Entry]
Type=Application
Encoding=UTF-8
Name=MPlayer
GenericName=Multimedia player
Comment=Multimedia player
Comment[de]=Multimedia-Player
Comment[es]=Reproductor multimedia
Comment[fr]=Lecteur multimedia
Comment[it]=Lettore multimediale
Icon=mplayer.xpm
TryExec=gmplayer
Exec=gmplayer
Terminal=false
Categories=GTK;Application;AudioVideo;Audio;Video;Player;TV;
MimeType=application/ogg;application/x-ogg;application/sdp;application/smil;application/x-smil;application/streamingmedia;application/x-streamingmedia;application/vnd.rn-realmedia;application/vnd.rn-realmedia-vbr;audio/aac;audio/x-aac;audio/m4a;audio/x-m4a;audio/mp1;audio/x-mp1;audio/mp2;audio/x-mp2;audio/mp3;audio/x-mp3;audio/mpeg;audio/x-mpeg;audio/mpegurl;audio/x-mpegurl;audio/mpg;audio/x-mpg;audio/rn-mpeg;audio/scpls;audio/x-scpls;audio/vnd.rn-realaudio;audio/wav;audio/x-pn-windows-pcm;audio/x-realaudio;audio/x-pn-realaudio;audio/x-ms-wma;audio/x-pls;audio/x-wav;video/mpeg;video/x-mpeg;video/x-mpeg2;video/msvideo;video/x-msvideo;video/quicktime;video/vnd.rn-realvideo;video/x-ms-afs;video/x-ms-asf;video/x-ms-wmv;video/x-ms-wmx;video/x-ms-wvxvideo;video/x-avi;video/x-fli;video/x-theora;video/x-matroska;

here is : /home/foo/.kde/share/mimelnk/application/ogg.desktop
[Desktop Entry]
Type=MimeType
MimeType=
application/ogg
Icon=netscape_doc
Comment=Netscape mplayerplug-in 3.45
X-KDE-AutoEmbed=true
X-KDE-nsplugin=true
Name=Ogg Vorbis / Ogg Theora

here is : /usr/share/mimelnk/application/ogg.desktop
[Desktop Entry]
Encoding=UTF-8
Type=MimeType
MimeType=application/ogg
Icon=multimedia
Patterns=*.ogg;*.OGG;
# Previous name of this mimetype
X-KDE-IsAlso=application/x-ogg
X-KDE-PatternsAccuracy=80
Comment=Ogg Multimedia
Comment[ar]=وسائط Ogg متعددة
Comment[az]=Ogg Multimediya
Comment[be]=Мультымедыйны файл Ogg
Comment[bg]=Мултимедиен файл Ogg
Comment[bn]=অগ মাল্টিমিডিয়া
Comment[br]=Liesvedia OGG
Comment[ca]=Multimèdia ogg
Comment[cs]=Ogg multimédia
Comment[csb]=Mùltumedialny lopk Ogg
Comment[cy]=Aml-gyfryngau Ogg
Comment[da]=Ogg-multimedie
Comment[de]=Ogg-Multimedia
Comment[el]=Πολυμέσα Ogg
Comment[eo]=Ogg Plurmedioj
Comment[es]=Multimedia Ogg
Comment[et]=Ogg multimeedia
Comment[eu]=Ogg multimedia
Comment[fa]=چند رسانه‌ایOgg
Comment[fi]=Ogg-multimediatiedosto
Comment[fr]=Multimédia Ogg
Comment[fy]=Ogg Multymedia
Comment[ga]=Comhad ilmheánach Ogg
Comment[gl]=Multimédia Ogg
Comment[he]=מדיית Ogg
Comment[hi]=ऑग मल्टीमीडिया
Comment[hr]=Ogg multimedija
Comment[hu]=Ogg hangfájl
Comment[id]=Multimedia Ogg
Comment[is]=Ogg hljóðskrá
Comment[it]=File multimediale Ogg
Comment[ja]=Ogg マルチメディア
Comment[kk]=Ogg Multimedia файлы
Comment[km]=ពហុព័ត៌មាន Ogg
Comment[ko]=Ogg 멀티미디어
Comment[lb]=Ogg-Multimedia
Comment[lt]=Ogg multimedija
Comment[lv]=Ogg multimēdija
Comment[mk]=Ogg-мултимедија
Comment[mn]=Ogg Мултимедиа
Comment[ms]=Multimedia Ogg
Comment[mt]=Awdjo OGG
Comment[nds]=Ogg-Multimediadatei
Comment[ne]=अग मल्टिमेडिया
Comment[nl]=Ogg-multimedia
Comment[nn]=Ogg-multimedia
Comment[nso]=Media wa Bontshintshi wa Ogg
Comment[pa]=Ogg ਬਹੁਰੰਗ
Comment[pl]=Plik medialny Ogg
Comment[pt]=Dados multimédia em formato Ogg
Comment[pt_BR]=Multimídia Ogg
Comment[ro]=Fişier multimedia Ogg
Comment[ru]=Звуковой файл OGG
Comment[se]=Ogg-multimedia
Comment[sk]=Multimédiá Ogg
Comment[sl]=Večpredstavnost OGG
Comment[sq]=Media nga Ogg
Comment[sr]=Ogg мултимедија
Comment[sr@Latn]=Ogg multimedija
Comment[sv]=Ogg multimedia
Comment[ta]=ஆக் பல்லூடகம்
Comment[te]=ఓగ్ బహుళ మాద్యమం
Comment[tg]=Мултимедияи Ogg 
Comment[th]=แฟ้มเสียง Ogg
Comment[tr]=Ogg Çokluortam
Comment[uk]=Ogg-аудіо
Comment[uz]=Ogg мултимедиа
Comment[ven]=Zwavhukwamani ha Ogg
Comment[vi]=Đa phương tiện Ogg
Comment[wa]=Fitchî multimedia Ogg
Comment[zh_CN]=Ogg 多媒体
Comment[zh_HK]=Ogg 多媒體
Comment[zh_TW]=Ogg 多媒體
Comment[zu]=Onozindaba be-Ogg

running the kcontrol-->kde-coponents-->file association 
i found out the their is no application/ogg association.
their is audio/x-ogg one and it's associated with vlc.
(which works great, btw)

i'm attaching the command's full output.

are these warning relevant ?