wrong credential, reload error

[Albert Luo]

I am testing CAS 3.0.5. If a user input wrong password in the login
page, he will get a new page with a notice of "wrong credential", if
he hit "reload" bottom on the browser, the following error message
shows up: A general exception occurred while trying to access CAS.
Please notify your system administrator.

I tried some of the CAS deployers, they don't have such problem. How
can I remove the problem? Thanks.