I'm just starting out with TiddlyWiki and TiddlyDesktop.
I downloaded an empty wiki, changed the name of the wiki in the browser and saved it. Worked fine.
Then I opened the same file in TiddlyDesktop, added a new tiddler and tried to save it, but I just get this error message each time:

I have no idea what might be wrong, so any help is welcome, because as of right now, I can't use TiddlyDesktop at all...