Memorex External CD/DVD Recorder--Media not recognized

I have a Memorex 16x16 external CD/DVD recorder (dual-format, I believe the name also includes) that worked fine for months. Now, however, the drive is recognized (in My Computer) but I constantly get asked to insert media into the drive. There’s already media there! I’ve tried blank CDs, pre-recorded CDs (e.g., purchased music CDs), purchased DVDs, and CDs and DVDs I’ve recorded which worked fine in the past.

The Memorex site has links to about 5 downloads (drivers, firmware, I assume) but they all give page errors.

How do I get the media recognized again? Again, NO media of any type is recognized. I’ve rebooted many times, checked the connections, etc.

I’m on Win XP, up-to-date patches and such.

Clean the lens?