Sorry. I can't use Mesa for Serious Sam (also for SE), because is giving me an error about "Cannot set display mode". The problem seems to be the wrong texture format ARB=6. With the 3dfx ICD driver the texture format is ARB=2, but this driver don't suport multitexturing. It works fine in Quake III after I've changed color depth to 16bits.
Thanks to you if you can post in your "first" topic.
Problem solved for Serious Sam SE, but I don't now how. It just started with Mesa. Another problem with this game (random crashes) is solved. I presume is coming from using 16bits z-buffer, and not 8bits (8 for stencil ) in the old driver. I think it was a hack for my V3 3000.