So I decided to finally purchase Dawnguard and Dragonborn, but when I have Steam "go online" it has to update, only that update CONTINUALLY crashes, saying I need to make sure I have an internet connection...in the middle of downloading the update, no less.

NOT ONLY can I not buy these DLC, I can no longer play Skyrim (or any other Steam games) at all, now. Bethesda, you better get in touch with Valve. THEY ARE COSTING YOU MONEY!

Yes, I've already done as much troubleshooting as I can. Valve is no help. Nothing works.