Issues with Sony MW600 not pairing with Droid X

[LadyBlacksword]

Ok, to set the scene here:
I have a Droid 2 Global, which I bought myself a Sony MW600 Bluetooth headset for a few months back. My choice of headset was a matter of practicality- The ear buds of the standard type found on Bluetooth headsets don't fit or stay in my ears, but the little in-ear silicone ones work great.
So far, I've loved the little Sony headset. It paired up easily and happily with my Droid 2 the first time I tried it, and seems eager to connect any time I'll let it. Never a delay or problem.

My husband has a Droid X.
Up until this week, he's had a little LG headset, but he managed to lose it. So I offered to let him borrow mine until we can either find it, or get him a new one.

Here's the problem: It won't pair with his Droid X.
I've gone so far as to totally remove it from the list on my phone and turn off Bluetooth on my phone while he's trying to scan for it, and yes, I've put it and his phone in pairing/scanning mode over and over again, but his droid X cannot seem to find the little Sony Bluetooth. They have compatible Bluetooth profiles, so I'm at a complete loss.
And yes, it still pairs up fine with my phone on the first try.

Any ideas of a trick I don't know about?