You are the fifth person (including myself) to observe or report this problem.
In all cases, I have never been able to reproduce the problem.
In all cases, there was assembly binding redirection. Most cases involved upgrading from some version of DevEx 6.2.x to a more recent version of DevEx 6.2.x. Two of the cases involved upgrading from DevEx 6.3.1 to DevEx 6.3.2.
In all cases, the problem has been resolved by the customer electing to migrate to the latest version of DevEx 6.3.x (usually DevEx 6.3.3).
I believe (but can't prove it) that removing all versions of DevEx 6.2.x and then reinstalling the desired version of DevEx 6.2.x may also solve the problem. I believe that this is so because a customer had a reproducible case and sent me his entire solution, database, and version of DevEx 6.2.x. When I removed all versions of DevEx 6.2.x and reinstalled DevEx, I could not reproduce the problem.
If you still want me to work on this problem, I will need a reproducible case including the installer for DevEx 6.2.x.