Strange update information

Dear Folks,

Using DWMX, I have a navigation column as a library element, and a template
that contains the library element.

When I make changes to the library element and save the document, a
notification window opens saying:

Line 7 Col 62 : Closed a <meta> tag that was left closed

The entire library item contains no meta tags, and no tags are unclosed.
I get the same error message when updating the template file. The template
contains meta tags but they are closed as xhtml tags />

When I change sites, I get the same error, with no docs or any other windows
open except for the site.
I don't get the error when updating any files in any other site.
When I went back to the original site, updating the .lbi and saving *did
not* produce the error

Can you explain what has happened here?

Is there a corruption in a file here?
Is this a known error?

Cheers,

Steve