As a possible solution try disable all your extensions and watch what happens. Especially on the same site/s that previous gave you the same issue. If it suddenly work, it's one of extensions that's the culprit. You should be able to find out who by simply enable one at a time and test those sites again.
If this tests don't have any effect, your only chance to get this fixed IMO is a contact with F-Secures support. If you for any reason don't feel like talking in the phone with a representative I can strongly recommend their chat. Hope you get it solved.