NFR_Zeclic: no, i m not signing, just impossible to log, with the message, wrong name, and the name can have only letters and numbers...:(
Looks like a clear fault of WGT. With the "letters and numbers" rule, any account with more than that will indeed cease to be valid, a new account looks to be the only way to continue.
You might try to move WGT to changing your name, with would save your possessions but might mean a limitation in playing options.
Wonder how many accounts are subject to this nuisance(?)