Use Google Chrome? Suddenly found that your checkbox vanished so that you cannot select things, eg in mail, select an individual mail for deletion? They’ve gone. Disappeared.
Annoying, isn’t it.
A solution however appears to be easy, although I can only vouch for it in XP
Right Click on your Desktop, Properties , Reselect your theme , Ok, then reload the page in Chrome.
Here’s hoping this helps a few people!