That's interesting that you've experienced that.
I've just tried the command "sc config imapi start= disabled" IMAPI was turned from automatic to manual. I still get all(5) my DVDRW's show up without any problems.
actually, in my system IMAPI was set to "Manual" even before I used the command "sc config imapi start= disabled". "Manual" was the default setting. After I re-enabled it, using "sc config imapi start= demand" (and restarted it), the cd-writer appeared again, and IMAPI was back to the ''manual'' mode.