missing sent mail from October nnfolder+archive

[Mike]

Hi:

I've got the standard elisp to archive my sent mail in monthly files.
The files (mail and .nov) for October-2009 are in the archive
directory, but the group doesn't show up, and isn't recognized - like
I can't even respool an article to that group.

I've tried nnfolder-generate-active-file to no avail.

Any suggestions?
Further info I could provide?

Thank you.

--
Mike