Looks like you have "a" texporter plugin in max4.2's plugin which is not compiled for max4.
Make sure that you don't have any other texporter anywhere in your plugins search path. I recommend you to seach texporter in your computer and delete all texporter files with dlu extension. Then put Texporter3.dlu that you find in the above zip to your plugins folder.
If you are still having a problem, then please let me know. That means your's is a unique case that never reported before.