@TFrieden
Thanks for the tip, I now use a stack of 3000000 and Quake 3 works correctly.
There is still the random bug making the whole system hang with the sound "buzzing" and the only solution is to reboot via the button on the tower.
Execpt this annoying bug (actually, it may happen within 2 minutes or within 2 hours).
My machine: AmigaOne G3/800XE 512MB Ram and Radeon 9200Pro (128MB Ram).
Well, I say I have 512Mb RAM but if I ever go under 240MB free, AmigaOS crashes.
I'd like to find a 1GB module