Suddenly today my files lost association to the proper program (zend studio) on my windows 7 machine. I right clicked the file and chose “open with” and navigated to the program, double clicked it. Unfortunately the program never got added to the list of recommended or available programs in the previous window, so I could not assign it as the default program. However, I was able to navigate to other programs and assign them as the default, so the problem existed with the program I was trying to select. I believe there was an issue with the registry keys related to this program. I ended up running the program installer again and doing a “repair” and then it worked.