I'm happy that my suggestions works for you. But maybe you should thank mr. hmepas at thread
from whom I've got the solution!
Anyway, I am running Slackware 9.0 kernel 2.4.21rc1 with this IRQ configuration for 3 days now, and I do not have any significant performance loss. The only problem I notify is the sounddriver (i810_audio) which sometimes is not available to other applications. But then again, this module already has some known problems, it might be the driver itself.
Furthermore, USB, tv-card etc. work perfectly OK.