You might want to take a look at our Database Accelerator product:
http://www.qdabra.com/proddetail.asp?prod=QDBXL1 - it seems like it would fit your scenario rather well.
However, instead of storing the entire form into a single xml column, you would be shredding the tables in the XML into relational tables in the database. Although it is not usually supported, if you work extremely carefully you could then reconstitute the XML from the relational tables (to do this in InfoPath would require a good deal of code). This would give you the advantage of using SQL search and reporting functionality instead of mucking around with XQuery, which can get pretty complicated. Also, DBXL has a new feature set that allows you to run searches on the shredded database with either a desktop or a mobile client (PocketPC)!
Otherwise, I'm not sure why InfoPath is treating the data from the xml columns as plaintext. You would think since you are using IP2007 that it would recognize it, but I haven't worked much with this platform, so I'm not sure what to tell you.
Matt Faus / Microsoft InfoPath MVPQdabra® Software / Streamline data gathering to turn process into knowledge