Love this app, but whenever I focus on another app (in windows) and return to my browser where I am logged into Guacamole, the VNC window starts misbehaving (enter doesn't work, windows resize randomly on mouse movement). The solution is just to kill the tab in question and launch a new one, then everything begins working again.
I'm using FF. I've noticed this same behavior on all versions of Guacamole I've used (starting with the Java Only version). Currently using Ubunutu 11.10 and use OpenBox with tightVNC.
If you are switching windows using the keyboard (via Alt-Tab, for example), then most likely the Alt key is getting stuck.
What happens is Guacamole receives the keydown event for the initial press of Alt, but once you hit "Tab" and switch to a different window, this new window gains focus, and the browser never receives the corresponding keyup event. Thus, as far as Guacamole is concerned, you are still holding down Alt.
You can work around this by pressing and releasing Alt again once you are back in Guacamole. The extra keydown event will be ignored by the VNC server, and the final keyup event will fix the state.
This same issue will happen with any keyboard shortcut which causes window or tab focus to change.
It happens with any focus change. For example, outlook will send me message alerts and since Windows has ADD, it will switch focus to that alert momentarily. This will cause the issue I'm talking about.
I just tried using alt tab and your proposed solution, it didn't work. Going to test it in Chrome (I use FF exclusively, at present). If I don't see the issue there, I'll start disabling plugins to see if there's maybe a conflict there.
Problem doesn't appear to affect Chrome.
Spoke too soon. It does the same thing in Chrome. Just took longer to manifest.
I disabled all my FF add-ons and started enabling them back one at a time. At least one culprit appears to be FireBug. With that disabled, I haven't seen the issue again (30 minutes into my testing going back and forth from my guacamole window to other apps). The chrome issue may have just been me hitting a control character of some sort.