I am running 12.04.1 with the Ask Ubuntu lens installed as well as Firefox 15.
There appears to be a bug when selecting an option from the lens which launches either a new window of Firefox, or a new tab in an existing window; In the new window, the right-click context menu will not appear. Furthermore, in a window that was previously open, with functioning context menu, a new tab launched from the lens will stop the context menu from appearing in all tabs.
This behavior is consistent, however, I cannot replicate it with any command line launch of Firefox into a new window, or a new tab.
Is there any way to view, or to modify the command used by the lens to launch Firefox?