Repair Disk Permissions not working

I've been trying to repair my disks via Disk Utility and it always says that there is less then one minute remaining. Yet it never finishes.

My computer is always locking up, and when I need to force quit apps, they go away but are still open(dock says they are) so I can not use them unless I shut off my computer and turn it back on again. I can't log out because it just locks up in this case.


What's the problem?

PowerMac G5 Single 1.8 running leopard.