Fans

I have my G5 1.8 dual since January and for the most part I think its great.
Several times though while idle and connected to the internet, no screen saver, nothing running, my fans start up full throttle like they are taking off. A popup tells me I must restart my computer and the only way to shut down is with holding in the start button for a few seconds. After turning on again every thing is fine. I do repair permissions and have installed Tiger but this has happened even befor that install. Any ideas, thanks in advance.

Ron

See if this is you
http://www.experts-exchange.com/Hardware/Mac_Communications/Q_21320202.html

I experienced a similar instance on my G4 ,OSX 10.3.9.
I would log onto the internet via dial up connection and after 2 minutes surfing I would get a pop up telling me to resart. The only way I could restart was by holding down the power button. This happened awhile ago and I think what I did to resolve it was check my panic logs and found my logitech Navigator keyboard was causing some kind of conflict. ( I think it was the panic log where I found this was the problem). Anyways, I uninstalled and deleted all my logitech driver software, plugged my keyboard directly into the back of my G4 instead of through my usb hub reinstalled a updated revision of the drivers later and all is well. My fan didnt go crazy when this happed however.

So check your crash logs or panic logs see if you see any problems.
Hope this helps