Tracking down source of wrong interrupt 2.6.7.

I have an ITE raid card, which sort-of-works with my k7s5a motherboard. Using the GPL driver from ite.
(copy at http://www.mauve.demon.co.uk/iteraid.c)

It causes massive keyboard problems, complaining about keycode 0 being undefined.

I suspect this is due to interrupt 1 (i8042) somehow being triggered every time that 11 (it8218) is.

About 80% of the time.
Any clues about where in general I should start looking?