I'm really late with posting this, but its been the bane of my login since my hosting's creation. My username for my subdomain is my name here, but in lowercase (snes350). cPanelX, is, much to my dismay, case sensitive on this. I always type my name in caps (SNES350, as it is everywhere I've ever used it), since I took it from something that used it in caps. It takes 2-3 login retries for me to remember that it is lowercase, which is really annoying. I even had my password reset previously, because I was trying uppercase letters with the password I knew I set, and it obviously wasn't working.