/etc/rc.d/rc.local

This file is part of the startup in both Slackware and RedHat based systems. I'll check on Debian still.

It often contains a startup for gpm, the console based mouse selection programs. On many X-windows installations you need to kill gpm before starting X windows. Some distrobutions of linux now make this an integral part of the startx command, but if not, you need to do it yourself:

        gpm -k
and you may have to be super-user for that.