We've been using MJ since Jan 09. Just in the past 2 weeks we have started dropping calls both incomming and outgoing.
Mj keeps rebooting too. Have call tech support so may times I've lost count.
It sounds like your MJ dongle went bad or your having a computer problem. I would read through past forums on these problems and start with that. Try your MJ on a different computer and see what happens. If all is well look at your computer settings and troubleshoot from there.