This is a (possible) issue with your data it seems that you have a user that has no email address, can you check your users in BugNET and see if one does not? If not can you give it one (even a fake one) and see if you still get an error?
Also can you remember being able to create a user with no email address?
You are right on the money!!!
My account had no email associated, and all users that access the issues that i created it gave tha error.
I installed the Bugnet, and then changed to Active directory, my account was the first.
Dont have a clue why my account had no email, all others from AD had their email.
Thanks for all the help :)