Error upon sign up with previously used e-mail

I’m getting a 500 error screen upon sign up.

I suspect the error may be related to the fact that I have used the same e-mail on a different account I created an hour previously. I removed the e-mail on the other account and I’m now attempting to create a new account with the e-mail address.

It turned out to be a clash on username rather than e-mail. I have now chosen a different username. Do note that the form did inform me that the username was available, though it seems it isn’t in fact available.