Had this problem a few days ago as well — freezes and I have to CTRL+ALT+DEL to stop Quicken. Happens when I do all accounts as well as accounts individually. Have Super-Validated the file, made a copy, reset a few accounts — all to no avail.
Oddly, when I restart Quicken, most times the downloaded transactions appear so on some level it is working, just not wrapping up properly.