ASPNETCOMPILER(0,0): Error ASPRUNTIME: Object reference not set to an instance of an object

I also had this problem and it was not solved by any of the ideas mentioned previously. The problem was that somehow compresssion had been enabled on the subfolder of my drive containing the ASP.NET website. The solution is to right-click, choose properties and in the general tab, click Advanced and under the 'Compress or Encrypt attributes' section, make sure 'Compress contents to save disk space' is unchecked. Upon prompting do this for all files and subfolders (note it may take some time). Hope this helps someone.

OK. After wasting so many hours I somehow got to this blog: http://thesoftwarepractice.net/development-things/object-reference-not-set-to-an-instance-of-an-object

Turned off the McAfee Real Time Scanning and its works...