Hmmmm... i had a Google homepage problem just on one of my computers a few weeks ago. at random modules wouldn't work, etc. nor could I add modules. All I did to fix it was just reset the cache... (this was in Firefox 2). Maybe this was slightly related?

the resetprefs thing has been around for a while. here's the earliest mention i could find:
http://google.blognewschannel.com/archives/2006/04/26/stuck-on-personalized-homepage/#comment-45760
but i think it's been around longer. you generally have to use that if you run an inlined gadget that hides itself and has some sort of bug. that's the reason i've had to in the past anyway. I don't suppose that's really Google's fault, by definition inlined modules can do whatever they want javascript-wise.