First: I actually HAD asked the person who asked me if I wanted to try the game.
Second: I DO NOT have DirectX 11... it would seem that 10 ALSO causes the issue, which neither the person who invited me to join the game NOR the 3 people he asked knew.
That would be why I posted on the forums...
Thank you for your input, which was not actually needed.
As a last ditch effort I'd restored the default settings and it 'fixed' the problem. (When I initially started the game it gave me a message about being able to run DirectX 10 and did I want to change the setting, not knowing it might cause an issue I said yes)