h/w buffer stuck at 256 PT 11

I have searched the APAC for this problem and found several threads concerning trying to change the h/w buffer in PT11. However, no real answers.

I'm using an mbox2 and have turned off all other sound devices. When trying to change the h/w buffer in the Setup/Playback Engine the H/W BUFFER SIZE is 256 Samples with no option to change it higher or lower. I can go into the Hardware Setup and start the Setup App and change the h/w buffer size there but this requires a restart of PT11 and after restart the h/w buffer size is still 256.

Any thoughts or possible solutions.