A
Firefox hangs
100 MB of memory usage sounds suspicious. try uninstalling it with Revo Uninstaller.
Seeing the screenshots I think it's a virus. Do a scan using a updated AV(avira or avast) in same mode.
Or try a scan using this *housecall.trendmicro.com
Or try a scan using this *housecall.trendmicro.com

