Cognos administration error.

[pravallika]

When  I am try to access Cognos administration, the following error appears within a yellow bar at the top of the page:
"Unexpected exception while executing the XML pipeline process 'logic'" error

Also, When I turn the anonymous access to FALSE, it prompts to the home page asking for the credentials once I provide my credentials the page disappears and ask for the credentials again.

Env- cognos planning 10.1.1, windows 2008 64 bit R2.
Has anyone faced this error before. Any help will be appreciated