This is kindofa ridiculous post, but I Googled & couldn’t find anything, so this is primarily to help other people that might have this problem.
Adobe AIR apps will lock up (ie freeze) if you try to click a url (http link) in them and the Windows Installer service isn’t running.
I tested this with both in Twhirl (v 0.8.6 & 0.8.7) & Tweetdeck (v0.20b), on Windows 2000 (Win2k) SP4.
Typically if you start the service (either through the gui interface, or with a NET START MSISERVER run at dos or from Start-Run) after you’ve clicked a link, it’ll unlock the app.. but not always.
I have no idea why AIR needs to have the installer service running in order for it to connect to your browser (frankly I find it both suspicious & more than a little lame), but there we have it.
Hopefully this helps someone. And yes, this was a deliberately keyword heavy post :)