What I would do is take a checksum of the file when it works, and then take a checksum of the file when it doesn't work, and see if the checksum has changed.
If it has changed then that would lead me to think that either something (a program) is corrupting it, or you have issues with your hard drive.
If the checksum remains the same, and the exe errors then it's possible you have a memory fault or something on the machine is causing issues (i.e. virus or malware)