I stumbled on a way to crash excel in Workbook_Open while making an .xla It's still a toy project, so I've been able to just delete it and start over (and now I'm coming back with version control and baby steps.)
However, assuming I didn't have those options, how would I possibly edit the .xla remove the fatal code, since I have to load it to edit, and loading it crashes the editing environment?
This isn't exactly what you are looking for. But some advice during development.
I always work on my xla files as xls files until they are stable. That way if it isn't stable, I can just not enable macros on opening, and fix the problem, then close and reopen with macros enabled.
--EDIT--
I did some more research, because I was curious and because I remembered hearing about disabling macros on startup. Here is a link that says you can hold 'Ctrl' while Excel is starting, to start in Safe Mode. There is a bit of other information that is worth a read to see if it applies.
http://support.microsoft.com/kb/826922
--EDIT 2-- Another link that says holding 'Shift' might also do the trick