If you happen unable to change iGoogle theme no matter what you do, congratulations, you got yourself one iGoogle bug 😀
According to Paul from iGoogle Guide, here’s a couple of potential workarounds :
- Try clicking on the tab’s name, then try changing your theme. This rarely works though.
- Create a new tab, move your content over to the new tab, then delete the old tab. The problem seems to only affect one of your existing tabs, so creating a fresh tab will let you set a new theme.
Works for me 😉