The latest version of Firefox is extremely unstable within the Parallels VM. Almost immediately, most pages will not render properly. Facebook in particular is a problem. Parts of the page will not appear, or begin to duplicate. Restarting Firefox does fix this temporarily. Used to be this problem would occur only after long use; now it's happening nearly immediately. As much as I hate Chrome I'm having to use it because of the stability issues. Yes I know this is partially because of how Parallels renders the VM but other browsers are not chopping up like Firefox.