I had been having no luck connecting my MX-900 to my MAC using Windows 7 under Fusion.

As luck would have it, I had to reinstall my system and couldn't find my key for Fusion so I installed Oracle VirtualBox (btw: it's free)

I followed these instructions and it worked perfectly:

1. First, I used 'VBoxManage list usbhost' to get info on the device:

$ VBoxManage list usbhost

VirtualBox Command Line Management Interface Version 3.0.10
(C) 2005-2009 Sun Microsystems, Inc.
All rights reserved.

Host USB Devices:

...

UUID: c8ed4c9a-79c7-4f19-bedf-ec2297bc116f
VendorId: 0x4647 (4647)
ProductId: 0x1000 (1000)
Revision: 2.1 (0201)
Manufacturer: OHSUNG
Product: URCHID
Address: p=0x1000;v=0x4647;s=0x00000acf4822b145;l=0x04100000
Current State: Unavailable



2. Then, I disconnected the USB device. Next I got the ID of the VM I wanted to use this device on:

$ VBoxManage list vms
"Windows 7" {7054ae16-455a-4bce-ad59-42d9737dee1f}

3. And lastly, I added the filter with this command, using the ID of that last VM as the -target (with the VM shutdown, of course):

$ VBoxManage usbfilter add 0 -target 7054ae16-455a-4bce-ad59-42d9737dee1f -name "URC-MX-900" -action hold -active yes -vendorid 0x4647 -productid 0x1000

4. I booted the VM, plugged in the MX-900, and presto!! Everything is perfect.

No more grabbing another PC just to program my remote :-)