Firefox losing focus on textareas

Firefox losing focus on textareas

Since yesterday, while typing, Firefox 3.5 on my laptop running Ubuntu Linux x64 has been losing focus on various fields from textareas on webpages, to the address and search bars. It's not that it thinks the tab key is being pressed because it's not going to anywhere, it's just unfocusing everything. It's also not a hardware problem, as other applications are not affected.