It is generally easy on all platforms to remove the application itself:
rd /s "%appdata%\Songbird2"
(%appdata% is a system environment variable that will expand to your Application Data path)
rm -Rf ~/Library/Caches/Songbird2 rm -Rf ~/Library/Application\ Support/Songbird2 rm -f ~/Library/Preferences/org.songbirdnest.songbird.plist
rm -rf ~/.songbird2
After you've uninstalled and cleaned everything up, you're ready to download and install the code or a nightly build.
Follow the same instructions as above, except use "Songbird1" or ".songbird1" (as appropriate for your platform) instead of Songbird2/.songbird2
XULRunner includes a Profile Manager that will allow you to switch between different profiles and try a new fresh profile if you think something in your profile might be causing the error.
Switch to the installation folder and run Songbird -p to bring up the Profile Manager.
There's more information about using the Profile Manager on the Mozilla support site: http://www.mozilla.org/support/firefox/profile
Start > Run > Command >
C:\>rd /s /q "%appdata%\Songbird2"