buffer error pro tools

[anth]

I have a RME UCX and running PT10 on windows 7 64bit. The buffer is at 128 and works fine. Now, if I change it in the RME window (I want to use 2048 for mixing), it restarts pro tools which is fine but then upon reopening and checking setup->playback engine in pro tools, I get the following message:

"Your audio device is configured with an unsupported audio buffer size. Please select one of the following supported buffer sizes in the device control panel : 32, 64, 128, 256, 512, 1024 or 2048"

and then in the playback engine window, the buffer size is greyed out and sessions in pro tools don't playback.

I tried updating PT10 to 10.2 and updated the RME interface to the latest firmware and software drivers, but I still get the same behaviour.