During Install: unexpected Arabic text in Elevated Permissions Dialog … why?
Mixed localizations like this have been reported fairly frequently in Mountain Lion, Arabic being the most common.  Normally it can be fixed by just going to system preferences/language &amp; text/language and using the Edit button to remove Arabic.

Having only British English on that list may be risky, because the OS has no British English localization, so something else has to be used.  Try adding back at least English and perhaps some other languages and then restarting.  Or even adding back English and Arabic and then restarting and then remove Arabic and restart.