I've been annoyed about this for a long time. Forms that simply reject e-mail addresses with a + in them (perfectly valid according to the standards/RFC's - see http://www.faqs.org/rfcs/rfc2822.html 3.2.4 Atom - definition of atext).
Well - we need to add systems that allow you to set a valid e-mail with a + in but then fail.
I finally managed to register my systems profile using Blizzard's battle.net SystemCheck.
I've been trying to do this for a few years - without success - even with help from Blizzard support.
Analysis went fine - but sending the report always failed.
It always gave "There was a problem sending your system information to Battle.net":
Every FAQ on it suggests network issues or similar. This time I even got around to using wireshark to prove that the connection was OK.
Yesterday they finally sent me the real reason: Submission will fail if your e-mail address has a + in it.
Am mentioning this here since I didn't find it anywhere on google and I spent an awful long time looking.
So - if you want to register a beta profile on battle.net using SystemCheck then make sure you don't have a plus sign in your e-mail address.