Ha ... finally ... got it up and running.
System is running fast and stable. Netsurf without freeze (as you can see).
Only 3 problems left (actually 2 of those are the same as under 10.5.1):

- No QE/CI with my Quadro FX 3400
- Only one core recognized (I hope this is not the fix for the netsurf-freeze ... I hoped for a more elegant solution )
- Samsung S203B S-ATA DVD is not recognized (worked without problem under 10.5.1)

Any ideas on how to get my system really perfect ?

(A8N5X,Opteron 165, 2GB, Quadro FX3400)

Ah, and BTW ... THANK YOUUUUUU !