I wonder if your hand histories are in a language other than English. Please reinstall the PartyGaming software in English and if that doesn't help for new hands then attach one of the hand history files to a Support Ticket so that we can see what is wrong.
It's true, but I play with other language for 15k hands and PT4 worked normally. I have restart partygaming and PT4, and all this fixed alone. Are you sure that the problem it is the language ?
Hand history files need to be in English for PT4 to import them. If the histories are in English and don't import then please send one of them to us to check out as I suggested.