Direct this to Google, this is something the Ubuntu community can't handle, due to Google using an entirely different repository source than the Ubuntu community.
However, before you do that, check your extensions and plug-ins at the links below:
Remove all the extensions and plug-ins and if your problem is fixed, then re-add them one-by-one, until the problem is reproduced. After enabling an extension or plug-in, refresh the Facebook page using the blue arrow (or hitting F5) to see if the change in extension/plug-in was indeed the problem or not.
If removing all extensions and plug-ins does NOT fix your problem, then you should check with Google. If there's anything else open at the same time that uses Webkit technology anywhere along the line, this may cause a conflict, but this is a very unlikely case.