hi,

If you have interrupts at different priorities using the same bank, the higher priority interrupt, if it occur during the execution of the lower priority, will really screw it up.

It`s right. Anyway, the original poster uses different banks:

void timer0 (void) interrupt 1 using 3
//
//
// and
void com_isr (void) interrupt 4 using 2

With such way, any priorities of these two interrupts may not cause registers` conflict.
Another reason I see that somehow Vico used some functions besides ISRs in which register banks are [re-]defined as well. It may be case why after he deleted all "using"s, then problem gone.

Regards,
Oleg