I'm running Vista, and Spaz opens links in IE even though I chose another browser (like Firefox) as my default. How do I fix this?

This is actually a bug in AIR, and Adobe shares a method for solving this in their release notes for AIR 1.0

To workaround this problem, go to Start > Default Programs > Set Program Access and Computer Defaults, expand Custom, select the radio button next to the application you want to set as the system-wide default browser (for example, Mozilla Firefox) and apply the setting.