Importing Issues - AJAX Error, Invalid URL

I'm having trouble getting my content imported using Feeds. I've set up my feed importer and got it tied to my content type. I've tried the import two ways and both generate errors. I'm stuck.

Option 1 - Directly from Add Content:

There was a note in the interface that to import from a file, you then go to add new content for that content type. So I try this. There is a feed area at the top of my Add Content screen where I can put in a URL for my CSV file. And then hit Save. (Note that I had to make all of my fields *not* required in order to get this to submit). The result is this:

An error has occurred.
Please continue to the error page
An AJAX HTTP error occurred. HTTP Result Code: 500 Debugging information follows. Path: /batch?render=overlay&id=55&op=do StatusText: Internal Server Error ResponseText:

So.

Option 2 - Standalone Form:

I found this -- http://drupal.org/node/1573024#comment-5987736 This has you go to /import/ to get the file. If I go to this page, I find my importer. However, when I put in the URL to where on the server my CSV file is living... I get an invalid URL error. I've tried it with http://, without it... with slash, without slash (getting desperate). No go.

Why is this so hard? Am I missing something obvious? Any help would be greatly appreciated.

Thanks.