Pressing alt in Unity 2D should bring up the HUD - it doesn't do this over ThinLinc. Similarly, pressing meta should bring up the Unity search menu, which it doesn't.
Not sure what other fun effects this might have, for example with keyboard shortcuts.
Report to Ubuntu and then move to 3.5.0.
This is actually solved by adding +kb to xserver_args.
Reported on Launchpad as https://bugs.launchpad.net/ubuntu/+source/unity-2d/+bug/989688. Moving to 3.5.0.
We are tracking the upstream bug, but nothing happens. For this release, we won't have time to work on this, or enable XKB. Moving forward.
Will hopefully fix itself once we have an upgraded, XKB-enabled Xvnc.
Works fine with our new X server.
Both Alt and Meta brings up different search dialogs on Ubuntu 12.04 in Unity 2D with ThinLinc 4.0.0post-3937.