+ AA6YQ comments below
* That's a likely symptom of resource exhaustion, Windows misconfiguration, or a latent defect in Windows - which is why I posted the above advice.
I've re-read both my description and his. They seem complimentary. There may be an issue of semantics, and my choice of words to describe the issue may benefit from fine-tuning. I would appreciate some insight as to how our two reports are crucially different.
+ Hank reported the appearance of "not responding" in DXKeeper's Main window's title bar, and (understandably) misinterpreted it to mean that the Sync process was not proceeding. My advice is to let the operation run to completion, ignoring the "not responding" message.
+ You reported that unless you start DXKeeper alone after rebooting, DXKeeper never completes the Sync process. The fact that the Sync process runs to completion when your instance of Windows has been freshly rebooted is what points to a resource management or misconfiguration issue in Windows.
+ For the record, I frequently see the "not responding" message in window title bars -- including in the title bars of Microsoft applications. Letting the operation run to completion invariably succeeds.