What will create trouble when updating to a new system? Non-FOSS. You can take that to the bank.
If it's not the greatest vpn client of all time, its vmware, the greatest virtualization solution on the planet *cough*.
This time, vmplayer 2.5.3 actually starts up despite kernel 2.6.31. But the guest system is unable to grab the mouse.
Turns out that the version of gtk is "wrong", and the solution is to tell the player to use its own (why isn't that the default anyway?):
Add that to /usr/bin/vmplayer, and you're done. Until the next kernel update.
Update: Just as I said, till the next kernel update. Just did one, and vmware can't find the kernel headers anymore. The solution is simple: comment the above line, compile the modules, comment it out again.