file upload of unaccepted type produces strange error message

When uploading a non-accepted type of file through the file component, I'm getting an error message like this:

Files with the 'db' extension are not allowed, please upload a file with a gif, jpg, png, 1, rtf, pdf, doc, avi, mov, mp3, or zip extension.

Note the "1". Sometimes there are more "1"s in the list - I assume it depends on which types are selected. (The type list is correct and exhaustive to what I had selected, the "1" is extraneous.)