Another user has reported here: https://groups.google.com/a/googleproductforums.com/d/msg/websearch/zup8Ij1FtZ0/mYxcJqElKI8J that the issue of the theme changing back was resolved by temporarily reverting to the "old look" and then switching back to the new. Now that your iGoogle has reverted to the "old look", do you still have the option to switch to the "new look"?