We accept hotmail. It might be because of some special characters. Do you use + ?
It's the only sane and easy (but obviously not bullet-proof) way of catching spammers out.
I tried with my Gmail address and it worked fine. That address has no numbers in it. I used the same password. If you aren't prohibiting Hotmail addresses then it must be the numbers in the email address that are triggering some validation.
Regardless, I have access now. Looking forward to trying your product!