I have this issue too, with the following observations:
- airappinstaller is left as a zombie process when installing directly from the browser (downloading the .air, then installing works fine)
- actually, each install leaves several zombied airappinstaller
- This occurs in both Ubuntu 8.04 and 10.04 (others not tested) with both Firefox and Chrome
- This is most annoying - please fix! :-)
Which version of AIR runtime are you on ? Also which version of flash player are you using ?