Can't seem to find an exact fix for this problem. I reinstalled Windows 7 (64-bit version), and of course had to reinstall all applications. Verified I'm running Win7-64 bit, but now when I launch Photoshop CS5-64 bit, I only get an error message that says "System unable to find file specified", even though the file is listed in the proper place by Explorer. I'm able to launch CS5-32 bit version normally, but of course that version limits the RAM available to about 3GB and I have 16GB installed. I'm able to successfully launch Lightroom 3 in 64-bit mode.
I've tried uninstalling Photoshop CS5, rebooting and re-installing in a different location with a fresh download of CS5 from Adobe.com but still always the same error message that "System cannot find file specified" when launching.