I get this too. I have tried a few combinations for an email address and the system seems to register it but when clicking apply it says "oops, something went wrong". When trying again it says the username/email is in use!
Im putting it down to the fact my broadband is not installed yet (2 weeks time). However surely it should allow me to register an email address before hand?
Thank you for your post Maburgess2206 and sorry to hear you're having some trouble registering for a My Virgin Media account.
If you're fully installed and have all the details correctly this should allow you to register, please do let us know if you're continuing to have this issue and we can raise an IT ticket to have this investigated further.