In the past few days I have been plagued with an unexpected Firefox popup that warns me that my PC is infected and threatens action against me unless I phone them and pay a fee to have the threat removed.  I have run every Bitdefender scan but nothing is found.  My PC bemoes unresponsive but I did manage to get the attached screen shot.  My only solution is to turn off the power supply to the PC.  I have also run the Microsoft Malicious Software Removal Tool - It took over 10 hours but found nothing.  This suggests that the problem is not virus related but is instead a form of adware hijacking.
	Can anything be done about this?
