In order to get your MSB working over a USB connection, you need to install a driver to establish a virtual COM port (VCP) for your host operating system. Specifically, download and install the appropriate VCP driver from http://www.ftdichip.com/Drivers/FT2232CDrivers.htm (the USB adapter uses a FTDI chipset). This software is the glue that makes the USB connection look like a regular serial connection.
Mac OS X
[[User::Bdferris|I've]] had some luck getting the MSB to work over USB in Mac OS X. What's more, the System Profiler utility (Applications > Utilities) was really handy for determining the Product ID and Vendor ID for the FTDI chipset in the USB adapter.
Installation is seemingly simple: copy both ftdi_ser.dll and FTDIPORT.INF into the Windows directory of your iPAQ. Reboot and then plugin your MSB. The iPAQ will prompt you for the name of the driver. At this point, you type in "\windows\ftdi_ser.dll" (note the full path, different than the FTDI installation manual instructions) and the driver will install and everything will be ready to go.
I ([[User::Bdferris|bdferris]]) had issues installing my FTDI VCP driver on my iPAQ. I finally ended up doing the following to get it to work:
1) Uninstalled the SocketCom Serial Card drivers for the old serial port card I had installed (not sure if this is actually necessary, but I did it)
2) Per the instructions in readme.txt included with the FTDI VCP driver, added a line to the FTDIPORT.INF file for my specific Product ID and Vendor ID for my USB device. The VCP driver reads configuration values from the INF file on bootup. The INF specifically specifies the PID and VID that it will install entries in the Registry for. By default, the specified VID and PID are 0x0403 and 0x6001, respectively. However, I determined (see #Mac OS X notes) that my PID was in fact 0x6010. So I added a few lines to my FTDIPORT.INF file to get it looking like this:
[FtdiHw] %VID_0403&PID_6001.DeviceDesc%=FtdiPort232,FTDIBUS\COMPORT&VID_0403&PID_6001 %VID_0403&PID_6010.DeviceDesc%=FtdiPort232,FTDIBUS\COMPORT&VID_0403&PID_6010
Basically, I just added another line for my specific PID. I copied over the file, reboot the device, and then proceeded with installation as normal and everything works like a champ.