CSV Importer Error

I'm using Omeka 2.0 with the latest CSV Import plugin. The csv file (UTF-8) imports fine unless I include the file column so I believe that's where the problem is. My URL is formatted like this:

http://bknotes.gmu.edu/plugins/Dropbox/files/366235.pdf

My error log shows this:
'Omeka_File_Ingest_Exception' with message 'Could not transfer the file from "http://bknotes.gmu.edu/plugins/Dropbox/files/366235.pdf" to "/var/tmp//a439a9045d8a2061df4a0fbaa746a13f.pdf": Unable to Connect to tcp://bknotes.gmu.edu:80.
Error #0: php_network_getaddresses: getaddrinfo failed: nodename nor servname provided, or not known' in /opt/htdocs/omeka-2.0.4/application/libraries/Omeka/File/Ingest/Url.php:68

This is a test CSV file with just 4 rows and the PDFs I'm trying to import are under 1.5 MB.

Any ideas?

If I remember right, the php_network_getaddresses error is due to something not right in how the DNS is set up on the server

Hmm, well the weird thing is it was working two days ago. I don't know what would have changed between then and now. Can you point me to more info on how the DNS should be set up?
Thanks.