The USB cable is pretty much standard.
I use the same USB cable to download to my smart phone as I use for my mx-950.
It most likely is due to active sync.
Sometimes my active sync doesn't want to connect with my remote, and I have to plug it i n and out a couple of times for it to connect.
The current version of active sync I have is 4.2 , which I believe is the latest( I upgraded it from the cellphone CD install).
You may have to go to MS site to get the latest version of active sync.
Reinstall the mx software, and then install, upgrade, and work on active sync, since that is where your cause is most likely.