The ticket supplied was invalid

 HI,
I've a web application developed using Visula Studio 2005 and C#.
One the server on which it is deployed has Windows 2003 and IIS 6.0
The Application uses Forms authentication using Custom authentication code.

It was working fine and suddenly after a new code deployment i am unable to Log in. As soon as login button is clicked it takes me to a custom page for Session Time out.
I checked out the application log to find  out this message
"Event code: 4005
Event message: Forms authentication failed for the request. Reason: The ticket supplied was invalid.
Event time: 4/9/2009 6:38:41 PM
Event time (UTC): 4/9/2009 1:08:41 PM
Event ID: ed6d3f80ae414e7cb4a77f4b4cd4967a
Event sequence: 46
Event occurrence: 14
Event detail code: 50201
 
Application information:
    Application domain: <some path>< ...