Lightroom cc 2015 won't export

I upgraded to LR cc, and it now won't export. I get an error dialog that reads:

An internal error has occurred: ?:0: attempt to index a nil value.

I read that this indicates that the program lacks permission to write to the location, which makes sense, because it also said it lacked permission to unzip a file when I tried to install a plugin. It makes no difference what output location I use.

It seems to be catalog-specific. I opened one smaller catalog, and that one worked, but my main one won't.

Does anyone know what to do about this?

Thanks

Dan

Just spent a very long time on chat with adobe support. It was a catalog problem, but that wasn't obvious. The agent first tried changing permissions in windows, but nothing worked. I then restored my catalog from my last backup, and that worked. He then created a new catalog and imported my most recent, malfunctioning catalog into it. the new one seems to be working.

I googled and found postings about this problem since at 2011, but none had the solution.

I'm glad you got that sorted Dan