APE locks up and requires IIS restart

[zenStudio Profile]

We are having to restart IIS several times a day for Helicon APE to work properly. This has been going on for more than one year. The problem is that a valid username/password is rejected by the username/password popup in chrome or firefox, but if I restart that web site in IIS on the server then that same username/password will work immediately again. Please advise. Thank you.