I know this is an old thread, but just recently had this problem, and hopefully this will help someone else.
I traced it back to a program that I was using to Overclock my system. It was EasyTune 6 that was not handling the memory timing in the overclock, and was screwing up the bundling. After removing Easytune 6, the problem disappeared. Tuns out it was corrupting anything memory dependant.
To the above post, you can use both mono and stereo files, but they cannot be bundled. Use per project saving, and it works fine.