It depends on the name you're using. It has to be in the Latin alphabet, not using any disallowed characters (.&* etc.) If you keep the name to a-z, A-Z and 0-9 you shouldn't have any problem. (It could also be too long or too short - it has to be between 6 and 30 characters.)
The only other thing I can think of is that the name you're trying to use is already being used by someone else.