The web server process that was being debugged has been terminated by IIS

Trying to debug the Sharepoint Application you might run into the message:
The web server process that was being debugged has been terminated by IIS
This can be avoided by configuring Application Pool ping setting in IIS

To setup app pool be sure that you are modifying the right one.

1. In the Application Pools list, right-click the name of the pool your application runs in, and then click Advanced Settings.

2. In the Advanced Settings dialog box, locate the Process Model section and chose one of the following actions:

   1. Set Ping Enabled to False.

      —or—

   2. Set Ping Maximum Response Time to a value greater than 90 seconds.

   PS. Found very useful an article about the debugging for sharepoint site:

   Simplifying SharePoint debugging by creating the troubleshooting toolbox