When I updated to Protools LE 6.4, my HUI (or other control surface) no longer works or shows up as an option in the Periperals/Midi Controllers window.
Dowload the legacy control surface drivers from
digidesign.com . It's somewhat tricky to find. Here's a listing of links in order to get to those drivers.
1. Click "SUPPORT"
2. Click "Downloads"
3. Click "Pro Tools LE 6.4 Updates"
4. Click "Download & Details"
5. Click "Pro Tools LE 6.4 Plug-In Updates"
6. Click "Legacy MIDI Controllers"