This error is inconsistent in the ways that it manifests itself. You are indeed right, it is very weird.
I had never had this problem before, until I installed the Blog on a Portal running under IIS7. At least, weirdly enough, it is the only box I had this issue with.
In your case, it could very well be that your host upgraded - or some other configuration was modified on the server.
The blog still runs under ASP.net 1.1 - and while ASP.net 2.0 supports and runs 1.1 it seems that it gets "STRICTER" in some combination of configuration (could be IIS7?).
At any rate, as Alec pointed out, this has been fixed in the current code-base that should make a release at the end of this month, but for now, look for the weird looking "e" in the ResourceKey attribute in the EditEntry.ascx file and replace it with a "normal" looking "e" :)
I hope this makes sense and of course, it helps!