As suggested by ElDiablo ..., your problem may be Virex. Uninstall it if you have it using its uninstaller if you can find it (I thought it was on .Mac, but now can't find it there). Originally, the fan problem was not associated with pBooks being plugged in and using Virex. But, now I have seen a report indicating the the problem only occurred for the poster when the pBook was plugged in. Uninstalling Virex was the fix. If you don't have Virex, use Activity Monitor to ferret out any app hogging way too much processor and quit it. If everything is OK for a while at least, then you may want to uninstall the app. On the uninstaller, it may get installed when Virex is installed. Also, it may be in the Virex disk image.