I've been seeing this problem a lot with WF5/WC9.x. I looked at the processes with Sysinternals Process Explorer and sometimes see 16 byte IO blips at 5 second intervals from xtop.exe, but sometimes not even that. No I/O, no cpu, no Reads/Writes of any kind, no CPU time change.
Normally I kill the xtop.exe and nmsd.exe and start over, but the last time I killed only nmsd.exe which resulted in everything working correctly. Not sure it's a long term cure, but it beat starting over for the 100th time.
I don't think it's a basic flaw in the software, but poor handling of some communications error condition that results in waiting for a message that will never come. Rather than timing out and retrying, it just waits.
