Mac Mini Freezing

Here is my setup. Core 2 Duo 1.83 Mini Stock. Connected via firewire is a WD Caviar Green 1 TB drive. My unibody 15in backs up wirelessly to this. Here is my dilemma: I just bought the external last week so it's the first time I've backed up. My mini has been hanging up recently causing me to have to reset the pram 1 about once every other day. When I try to shut down it says something to the effect of "Safari or quicksilver has refused to quit, shut it down and try again. So then I have to hold the power button. Then it won't turn on so I reset the pram. And so the cycle goes. I haven't had these problems prior so could it have something to do with TM?

I stopped automounting the backup disk on my MBP, and unchecked the put disks to sleep box. I don't know for sure but it seemed like my TM disk would sleep and not respond causing the lockups.