Answer
Normally, when there is an error in the Event Viewer saying that w3wp.exe has crashed, this means that your application pool has crashed. So, by extension, anything running on IIS will stop working. There are many reasons why this could happen, so to find out the root cause, there are a few things that you can do:
Look at the dump file generated by the Event Viewer
that is tied to this specific error.
Run this file through WinDbg to get a stack trace of the
error.
These two things should give you the information you need to determine the root cause of the problem. Below is an online article explaining in more detail how to get these two things and possible causes of the crash.
http://blog.whitesites.com/Debugging-Faulting-Application-w3wp-exe-Crashes__634424707278896484_blog.htm