new batch limit of 256 files in Acrobat Pro 8 and 9?

I've recently encountered a problem where Acrobat Pro (8 and 9) will not batch process more than 256 files. It will process up to 256 files, then generates error messages that it cannot open the remaining files because it thinks they are already open. It is as if Acrobat Pro starts tripping over itself and can't remember which files have been already opened and closed. Once the error occurs, there is no way to rerun the batch sequence without shutting Acrobat down and restarting it.

I've been doing these types of batch operations for the last 5 or so years without problem. The problem cropped up this year and I've been able to reproduce it on 2 different computers ... one with Acrobat Pro 8 and one with Acrobat Pro 9. Both are running Windows XP SP3.

At first, I thought it might be something corrupt in some of the files, but the following experiment ruled out that possibility.

I used Acrobat Pro 9 to create a blank, one-page pdf.
I then used the following DOS command
for /L %f in (1,1,300) do copy D:\batch_test\blank.pdf D:\batch_test\%fblank.pdf
to create 300 identical copies named 1blank.pdf, 2blank.pdf, ..., 300blank.pdf .
Each file was 6 Kb in size.

I then ran different batch operations (count number of files, count number of pages, number pages) on the folder containing the 300 blank files using the batch processing utilities accessible from Advanced > Document Processing > Batch Processing. Some were simple javascript executions others were the built-in batch commands that come with Acrobat Pro.

In all cases, the batches processed 256 files and then stated that they could not open the remaining files.
The stated reason that it could not open the remaining files is that they "are already open."
When I looked in the output folder (a different folder from D:\batch_test) designated for the batch operation, I found 256 files had been processed.

Has anyone else encountered a similar limit?

I'm not a programmer, but I recall 256 being some type of array limit for some programming languages and wondered if this might be related to the cause.