IIRC OnGame do not write the mucked cards to their hand history files. They are stored on their servers, which is what their hand history viewer uses, but not in the version which is written to your computer.
If you have a hand history file which includes mucked cards which aren't imported to PT4 then please attach it to a
Support Ticket with a note of the hand number in question and we'll investigate.
TableTracker searches are working for me at OnGame - can you tell me exactly what isn't working? What stakes are you searching for?
(Note that site launch and table opening isn't supported at OnGame.)
We submit PokerTracker to the assorted anti-virus suppliers, but sometimes it can take some time for their definitions to be updated.
As long as you downloaded PT4 from this website it is a false-positive and can safely be ignored.