Yeesh... Talk about a minor panic.
Don't ask me how, because I'm not entirely sure what I did to make it happen. But, I thought I went to commit some code, and when I hit 'commit', instead of committing the code, it decided that I had flagged my entire working directory and the point in the repository for deletion.
I really don't know what happened.
I thought I'd fix the problem by simply pulling out my stuff at a previous revision, and recommitting. This seemed problematic because I'd have to re-add the trunk, and there would still be a delete in the history, and I'm sure that could cause merge-hell in the future.
Some quick googling turned up Tim Hatch's very simple instructions on how to rollback an SVN commit. Tim apparently accidentally checked some confidential information into his public repository and explains how to rollback a revision by doing something really dirty: manually modifying your repository.
I won't rehash what he explains, but know that his solution worked for our FSFS based repository.