Tried looking elsewhere for this but just not finding anything.

When I try to create an account to play the game I get "Error: invalid user name". Tried many different configs, simply not working. Any help?

There's one guy with the same error in the French part of this forum and he eventually succeeded. Just keep trying perhaps? Not a great solution but maybe enough for now?

I have the same problem, tried many times as well and it does not work yet...

Same here..

Windows 8 Pro
Steam

Tried to "run as admin"

Tried nearly 100 random Names

Nothing works, plz help

*Edit: Looks like there is a Problem with field GUI_REFERRAL ....what Kind of Information i have to enter there ?

Sounds like you need to enter a coach name there. You could try entering
pmcc

He's currently the main programmer for the game and he has a valid account with that coach name. Of course, you can enter any coach name you like. I don't know if it will accept any text or if it checks whether the name actually is a valid coach name.

The referral thing is explained here: viewtopic.php?f=8&t=1196

Thanks, ONLY that Coachname worked.....nothing else......thank you.......

but i dont understand it

could you explain why it has to be so and where i should known ?

The referral thing is meant to reward those players who recommend the game to others and get them to buy Dungeonbowl. When they create their own account, they can enter the coach name of the friend who recommended the game to them. When the friend gets two such referrals, he gets a free DLC and so on. I know this works because two of my friends have entered my coach name into the referral field and I have gotten a free DLC code.

It should NOT be so that you MUST enter a coach name into the field to be able to create an account. You should be able to leave it empty. This sounds like an error in the system.