I'm using Suse 9.0 and when I start X, the mouse pointer moves. However when I start the window manager the pointer freeses and never unfreeses. I'm using a PS2 mouse (ps/2 autodetect on dev/mouse, where /dev/mouse points to /dev/psaux)

I've tried several types of ps2 mouse devices in sax2 (which works ok) by the way, to no avail.

Any ideas? Because I just do not know where to start.

Just the mouse freezes? Can you check the last few lines of the log file /var/log/XFree86.0.log for errors?
Also have look at the file /etc/X11/XF86Config-4. There are probably a few lines in there like

# sw_cursor is needed for some ati and radeon cards
#Option "sw_cursor"
Option "hw_cursor"

You could try swapping software and hardware cursors there (just move the # to the other line).

You may be able to free up the cursor by swapping consoles. Do Ctrl-Alt-F1 to get a text console and then go back with Ctrl-Alt-F7. This is at least better than killing off the wm.

I had occasional mouse lockups with KDE 3.1 and had no solution until a kernel upgrade to 2.6 series fixed everything.

No this doesn't help

I'm not trying to sound naggy, but it is not specific for one wm; windowmaker, and fvwm2 have the same problem too.

Well, if nothing from those suggestions I am stumped. Some long shots: check if gpm (the console mouse driver) is running. If so killing it ('killall gpm') might have some effect. Have a look in the BIOS for anything to set/change.

Otherwise try a USB mouse (MS mice come with a ps2 to USB adapter) or upgrade to kernel 2.6 which I understand has a completely different way of handling input. Or just google for similar problems.