How does your LabVIEW code call the .txt file? Is it a hardcoded path, or a relative path? I have a feeling that when you create an executable, it's either looking for a directory which doesn't exist (like the National Instruments directory which most likely doesn't exist on a PC without LabVIEW), or a relative path which is different on the target PC.
I've made executables which look for text files, so I can tell you that it can be done (both reading and writing).
Mark