Midi to USB cable from TB

I purchased Turtle Beach's Midi to USB cable several months ago and it
worked perfectly, allowing me to use an old MusicStar keyboard to play
around with recording in MidiSoft, etc. For some reason the connection no
longer works. I've read their online FAQ, uninstalled-reinstalled numerous
times, etc., but the TB Device Status program does not recognize the
keyboard. Device Manager has a question mark in front of "TUSB3410 Boot
Device"; there is nothing about TB in the Sound, Video, and Game Controller
section.

I tried installing on a different WXP computer and ran into the same
problem. I connected the keyboard via the original joystick/serial port
cable to an old W98 box and the keyboard works fine.

Any suggestions?