I used YADB a bunch this evening and finally put two and two together. MC only sees my Internet connection if I have very recently used it (and ripping a CD takes long enough for it to no longer think I am connected). I had noticed this previously when starting up (got the you must be connected to load this page error) but ignored it. For what it is worth, Quicken (2005 version) has the exact same problem so I don't know if it is an MS issue, a Windows SDK/API/DLL issue, or a weird system issue.
Details:
I use Firefox as my default browser, not IE.
I get consistent, repeated failed to connect errors to YADB with no evidence that a connection was ever tried (from your logs).
Tonight I was using YADB repeatedly and getting the constant errors.
Once it dawned on me what might be happening, I Alt-Tabbed over to FireFox - refreshed the current page - went back to MC and YADB connected instantly. This was almost 100% repeatable. If I had a connection issue, refreshing my current page in the browser would almost always get me an immediate fast response from the YADB server.
Still don't know why I have this problem, but at least I know how to 'fix' it for now.