So... I just spent the last hour or two pulling my hair out trying to figure out why none of the full-text searches were working on a specific table of my database. (SQL Server 2005 Express with Advanced Features). Here's what I learned.
Problem: SQL Server full-text search will not index new rows after a certain date. After dropping and rebuilding the index all full-text searches return NO results on that table. When this happened, it was only happening on one specific table and all other tables were acting normally. I eventually dug way down into the SQL full text error log and found an error like this: "Error '0x80040e09' occurred during full-text"... This happened after switching to a new database server.
Solution: Reboot the server. (Are you kidding me?)
Hope this saves someone an hour or two.