Random Sleeping When Encoding with iDVD5

Having a very odd problem which I'm hoping someone else will have experienced so I can figure out why it happens.. When I have iDVD encoding an AVI video to DVD my iMac G5 (bought at the start of April 2005) randomly keeps going into sleep mode even though I have it set to never sleep, often while I'm in the middle of doing something else such as typing this..

Only seems to happen with AVI's and doesnt occur with every one. If I close iDVD the Mac operates fine. I'm currently using the DivX Fusion Beta 2 to allow me to load AVI's into iDVD although I have had the same issue using DivX v5.1.1. I can play the file perfectly fine in Quicktime Player under the same codec without the Mac going to sleep so it appears the problem is with the iDVD app..

I'm hoping someone else will have experienced this problem and found a solution as its proving pretty frustrating..

 

Is there a program that displays the CPU temperature on the G5? I've found the miniCPUheat widget but the release notes state it does not read the temperature correctly on the older G5's which I guess is what mine comes under as it was manufactured prior to the late-April 2005 product refresh.

 

When encoding the temperature from miniCPUheat shows as 103C compared with 93C normally (both seem high to me which may confirm that the widget does not work correctly with my G5 although saying that I dont know what the normal operating temperature of a G5 iMac should actually be..)

 

Thats what I thought but the 93C temperature thats reported without iDVD running is still pretty high which is why I'm thinking my G5 is one of the models not supported by miniCPUheat.

Do you know of an alternate program that is likely to work so that I can confirm the temperatures?

 

Tried using a program called X Resource Graph. CPU T-Diode reports 70C without iDVD loaded and up to 80C when encoding, machine enters sleep mode at 83C. A bit of google'ing gives the normal operating temperature of the G5 as between 50C and 90C so it's seeming more and more as if my G5 might be faulty...