I am not sure if you've experienced the same problem when using Arduino IDE under ubuntu.
When I am editing a sketch in Arduino IDE, it seems the program is not responding to what I type from my keyboard.
But the Arduino IDE is not frozen, as I can use my mouse to click the menu bar, and eg save the file.
This happens randomly, sometimes it never happens for a day, but sometimes this " no response" happens every 5 to 10 minutes.
What I can do is to use the mouse and save current sketch, and restart the IDE again.
I am using latest Arduino 0017 I found same problem in Ubuntu 09.04 and 09.10