Can you try FireFox in safe-mode, so your extensions, themes and plugins are all disabled, and see if that does anything.

Also, if you use a larger than normal font-size in Beehive or in your browser can you try the default for both.

Using safe mode now and it's not here. However, when i logged in a minute ago and saw this post i was using normal mode and it wasn't there. It seems to be rather random. Font size is default for all.

Back in normal mode and it's still not there. Go figure.

Gone for me too now :{)