All my interrupt routines are ASM, ON INTERRUPT won't do as I need a REAL interrupts , not "I'll do it if I can" type. I'm sure that they are properly writen, they work fine if I don't utilise LCD. My interrupts are pretty fast, always in range of 200-1000 us and execute in couple of us. Problems manifests as displaying garbage on LCD, missing lines or some strange thing as shifting entire lcd to left or freezing it completly. Few time it even managed to reset PIC (had to increase WDT prescaler by far to get read of this).

I didn't know that commands take such long time (2000us). Is this a time to PIC to issue or LCD to process command? If second, I could manage to to overcome this. If first, it is the problem since my interrupt vould cut this command several times during execution.