How to solve Error: Cannot create file mapping in Ax2012 Enterprise Portal

Sometimes a perfectly fine, up and running Enterprise portal (Role center) will stop working and throw the below error.
Error Message: "An unhandled error has occurred. To view details about this error, enable debugging in the web.config file or view the Windows event logs. Go back to site."

You will generally get an error message like "Unhandled exception has occurred" or "An error has occurred. Contact your administrator for further assistance" on the Enterprise portal site or on the Ax Thick client (for role centers). But to have the understanding of the actual error, look into the Event Viewer (eventvwr).

Solution:
The solution that worked for me is quite simple to implement and you can give it a try even though you have some other issue related to Enterprise portal.

1. Go to System administration > Setup > Enterprise portal > Deployments
2. In the opened dialog, verify if the Deployment target is pointed to the correct folder (typically DynamicsAx)
   
3. And then click Deploy button, which will updates all static files, web controls, images, and proxy files for a specific Enterprise Portal site and also deploys new page definitions.
   

This will take little time but proved effective everytime for me. Hope this helps. Good luck !!