Hi Ryan! Carol at Trulia here. Listings that show Unknown are listings that have not been updated. If listings are manually submitted to Trulia and not updated from your My Listings page every 30 days, they will show Unknown. While they appear in your Unknown folder, you cannot resubmit a new listing for them.
You can log into your Trulia account and reactivate the listing by going to the Unknown folder and clicking on the red link, Delete listing. Once you have deleted the listing, go to the Removed folder and click on the "Restore' button for each listing that you would like to reactivate. The listing will return to your Active folder and update on Trulia within 24 hours.
If you have additional questions, please contact us at http://www.trulia.com/help/ask/
or call Customer Service at 1-888-466-3501.