So I started up X and the mouse wasn't working. When I killed the X server, I received the following message:

(EE) xf86OpenSerial: Cannot open device /dev/mouse
No such device or address

Which mouse is it? Serial, PS/2 or USB?
If it's serial in COM1, create a link (as root)
cd dev
ln -s ttyS0 mouse

For COM2, replace ttyS0 with ttyS1. For PS/2, replace ttyS0 with psaux. I'm not sure about USB.
Note: xf86config can put the right values into your X config files, too. I accidentally said earlier that the command is xf86setup, that's obsolete.

Did that ... got the same error message, including:

(EE) Mouse0: cannot open input device

(EE) PreInit failed for input device "Mouse0"

If your BIOS has a setting "USB keyboard/mouse controlled by" OS/BIOS, change it.

The mouse works fine when using XFree 4.1 ... it wasnt until 4.2 that came out that the mouse stopped working ...

I have no option like you mentioned in my bios

On another interesting note, cat /proc/interupts does NOT show my mouse ... so ... UGH!

The only thing I found that works was to buy a usb->ps/2 converter for my keyboard. When I plugged the keyboard into a standard ps/2 port ... suddenly Linux recognized my ps/2 mouse.

There's gotta be another way ... but ... hey, it works for now!