RoboHelp 10 error - could not rename file

I am trying to update a RoboHelp 10 project. When I make a change to a file and try to save it, I get this error: Could not rename file. xxxx<filename>.htm# to xxx<filename>.htm.

It seems to think the original filename is a .htm#. But the topic properties say the filename is just .htm.

I did get a new PC and backed up this project and then downloaded it to my new PC's hard drive. Could something have gotten corrupted?

Thank you,

Kathleen