> This started happening sometime between 1.5ZB and 1.5ZC. I am running
> -current from May 10th and XFree 4.2.0 built the day after.

The pms{i} drivers got united and rototilled.

> May 21 17:20:59 pesto /netbsd: pckbc: command timeout
> May 21 17:21:00 pesto /netbsd: pms_disable: command error

This is very interesting. It points to a possible solution - we could fall
back to reset the mouse in polled mode (blocking a lot of interrupts) in this
situation.

Could you update to -current and try running the mouse for a while with options
PMSDEBUG? This should print out delay timings that cause the regular resets
of your mouse interface.

Martin