Apple ID on iPod Touch

iTunes recently forced me to change my Apple ID from a name to my email address. No problem on my desktop computer, but my iPod Touch doesn't know this and whenever I try to log into my Apple account, my old ID goes in, which of course no longer works.

No point in requesting a new ID.... I already have one. No point in requesting a new password, as that is not the problem. All I want to do is access my Apple account with my EXISTING ID and password - on my second device.