I was generating a new character and rolling stats when a long internet lag occured. I lost connection, reconnected and found out that I can no longer generate that or any other new character due to "You are only allowed to roll one character at a time". Is there anything that could be done whith it? Am I to whait a fixed amount of time before I'll be able to generate any new character or is there a way to renew generating that one?

It was found that after about 15 minutes the character being generated vanished and so the problem was solved.

I don't know what the actual time out is, but 15 minutes seems about right.