Firefox is 14.01, ubuntu is 12.04 latest updates. Unity 3d.
Regardless of what I'm doing in Firefox menus will stop working if I open a web page from the HUD. If I run Firefox normally everything works normal, if I then open a link, say from the ask ubuntu lens, I'll be allowed to open one menu one time, after that all dropdowns (of any kind, also url bar searches) are gone.
This also happens in safemode so addons should not be an issue.