This morning I tried to start up Xcode but it crashed on startup.
The console revealed:
layout bitmap too short: ASKScriptView
After a bit of searching I found this blog post. Although the main post wasn't quite relevant, one of the commenters described my problem:
Xcode 3.1 has been crashing for me since the 10.5.5 update with an error saying "layout bitmap too short: ASKScriptView". I couldn't find reference to this online and was completely stumped.
Another commenter said:
just get the '/usr/lib/libobjc.A.dylib' from a 10.5.4 system (Look for it in a 10.5.4 combo updater file) and swap it with the newer version. Then, it works again.
So I searched on Apple's site for the Mac OS X 10.5.4 Combo Update.
But then I was stuck with a 561MB .pkg I just needed extract one file from and I had no idea.
More searching revealed the shareware Pacifist from CharlesSoft which I promptly downloaded. It worked like a charm and let me extract just the libobjc.A.dylib I needed.
Now Xcode starts up fine! Sending my $20 in to Charles...