Editor present but not loading

Yesterday, everything was working fine...I replaced an instance of FreeTextBox with FCKeditor in an ASP.NET application I'm working on. I modified fckconfig.js to add a custom toolbar set for it, which worked fine as well. I was able to use the editor fine in the application. Today, however, even though no code was changed, the editor no longer appears. It is defined in the source, and the iframe it sits in is present, but the editor is completely blank. I get a few javascript errors that show up, the first of which is from the first line of fckconfig.js, that FCKConfig is undefined. I cannot figure out why this just all of a sudden started happening. The only thing that I've done between when it was working and this morning when it was no longer working was that I added the FCKeditor folder structure to the project's source control. I've tried checking everything out to see if perhaps something being readonly was affecting it, but that did not help. Does anyone have an idea why this might be happening?

I saw a few posts that mentioned things close to my issue, but taking the suggestions in those have not corrected it. Somewhere I saw one mentioned that modifying fckconfig.js could cause it to happen, and I even tried to stop using my custom toolbar and replaced it with the old fckconfig, but that still did not work.