Developer Cannot assign tickets

[acidzfire]

I am new to Mantis and am using version 1.0.8. I am having a problem where developers are not able to assign tickets to themselves or each other.
Under Manage->Manage Configuration->Work Threshold I have it checked so that anyone with at least developer level can assign tickets. When I log into one of the developer accounts, I can not assign anything. I can change the assign field on a few tickets that have been resolved but not on anything new. We have many projects and are all set to private for differant reasons. Each of our developers are been added to each of the projects. I am able to assign them fine through a manager and administrator account.

Can someone give me some insight as to what may be wrong? If there are any files or screenshots that will help, I'll gladly post them.