Overwriting in batch processing

Switching from Audition 3 to CS6 has been problematic for me, in the Batch Conversion department.

In Audition 3, I could open many hundreds of WAV files, convert them in mp3, and the processor would then erase the old WAV versions.

Now, in CS6, I check the "Same as source file location", as well as "Overwrite existing files".

But that last one seems to simply...  not work!  After the conversion, I end up with both the new mp3 files, but also the old WAV files that I dont want.

What gives?  I know this is kind of a particular fonction, but anyone else can reproduce this problem?

Thanks