Hmmmm ... that's been a few years since I last loaded them in impulse tracker f00, so can't help you much with it. Sounds like not enough memory yeah, also make sure you use a driver with MMX filtering....
I'll see if I can dig up some more of my stuff from the internet .... too bad traxinspace is down :-\
There is one linux tracker I found, however it's not impulse tracker like. It's fasttracker like (handles XM files and it's own format (XM based with some other effects)). It's called soundtracker and you can find it at:
http://www.soundtracker.org/maybe I'll actually start doing something with music (read: tracking
) again .... my taste changed a lot though, used to listen to techno/house, now it's mostly rock music....