My error is that every time I try to play VMK, it goes through both of the loading screens. Then where it would normally bring you to the main map screen where you can begin to play, for me it is just black. I cant do anything except exit the game. This has been happening every time for me. I followed the instructions listed above, but it didn't work for me. Is there anyone I can talk to about this maybe? Writing the VMk help email has not been helpful at all.
I think I have the same problem as you, or at least how you've described it. I've wrote to VMK contact us several times but their responses were pretty much useless.
It seems to be something to do with accounts and nothing with shockwave or video cards (I can log on with my other account). If you can log on with another account as well, it shows that account, through friends list, with the black screen as online but not in any room.
Did you also hear a sound on that black screen?
I'm looking for a solution which I wrote some time ago when I had the same problem as well...