Before the 1.2 update I was able to make Skype video calls, but in GTalk I could only receive. It's the same now. I simply don't get the option in settings.
Perhaps it's an idea to delete the account in N900 and reestablish it? Have anyone tried that?
I guess first remembering disabling sync is a very good idea (I'm using Nuevasync).....
Video call works for me, at least on gtalk. Just choose the contact from phone book and there should be option for video call. But you need to be online to call. Oh, and receiver need to have video call feature too.