At my current job, I recently upgraded from Windows XP to Windows 7 64 bit. This was a very happy day as I had been waiting to get out of Windows XP, but this upgrade also meant I was going to have to test the applications I support to make sure they continued working. As expected I had a hiccup in most of the applications, but the hiccup was all traced back to one area, accessing Oracle. The wonderful error message I kept getting as shown below was like most error messages…so helpful.
So after some digging, I wondered if the application was having issues with the bit change on my machine, since I noticed the Oracle client that was installed had 32bit in the entry in the start menu. So I created an x86 profile based on AnyCPU profile in the configuration manager, and compiled and ran the applications, and SUCCESS it worked. So I asked IT if I could get the 64 bit version of Oracle installed, and as expected, they were unable to install it. So I got to make this similar change to all the applications.
Hopefully the fun debugging and troubleshooting I went through might help you if you come across a similar error/exception message.