IIS and Integrated Authentication

I have an ASP .Net application that runs on a Windows Server 2008 R2 machine that uses integrated authentication since all of my workstations are joined to the domain and all the users have domain accounts.  The IIS integrated authentication usually works fine, but every now and then when users try to go to the website, IIS will start prompting everyone for their network credentials and the website will not work even when users enter the correct credentials.  After some trial and error I have discovered that restarting the Windows Process Activation Service on the server where IIS is running will clear up the problem and integrated authentication will start working properly again.