In your case, it looks like the problem is with the G at the beginning of Gregair13. Try using gregair13
Actually, it's more likely the #. Spambots use text followed by 2 numbers often for the username, so it's blocked. Alt-O > Connect > Identd > User ID. Try without the number (also, like RusselB mentioned, you can just try with a lowercase G) and see if it works. This has no affect on what nick you use.