Page Not Found Message with a Corresponding Event Viewer Guid Error

The user sees a "Page Not Found" when going to certain pages. Sometimes, those exact pages are known to work for other users. The server Event Viewer message contains content simillar to the detailed error message below.

Steps To Reproduce:
Unknown. It is often the cause of cache in either a single computer or a proxy server on the network.

Clear the cache from the computer experiencing the problem and make an exception in the proxy server not to cache data for the Project Insight application. Loading pages from cache could prevent the users from seeing real-time information and cause errors such as this one. Clear any browser bookmarks to pages within Project Insight. Browser bookmarks may contain old session data in the bookmarked URL.

Affected Versions:

Detailed Error Message
Stack Trace:
System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.FormatException: Guid should contain 32 digits with 4 dashes (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx).
Online 8/26/2009