G5 OS10.5 freezing on startup

Hi everyone, hows it going?

The last couple of winter's when it's been a bit colder in the room my computer has had trouble's starting up. Usually it'll freeze somewhere along the startup routine, sometimes at the spinning clock symbol, sometimes once it gets to the desktop.

When i force shut down by holding the power button in and then restart - it'll load up fine. On the rarest of occasions 2 force restarts will be needed.

From time to time it'll give me the following screen:

http://www.willarbuckle.com/junk/screenfreeze.jpg

The computer also sometimes doesn't shut down either on normal shut downs. Can anyone help?

Thanks guys,
-Will

See if it will startup from a Mac OS X installer disc without kernel panicking. If so, then your HD may be failing or the OS installed is corrupted.