a. This problem was also reported for System 7.6.x about a month ago - right here on MacFixIt. However, based on email messages I have recently received, it seems to be much more widespread in Mac OS 8.
b. Brian Yamanaka writes of one possible reason this problem occurs on some Macs and not others: "On my 8500/180 with Mac OS 8 GM installed, I can no longer see my floppy drive after installing Ram Doubler 2 only if I have a video monitor plugged into the AV output of my Mac." (Still, I doubt this is the cause for every one who has this problem.) In any case, you might also try a clean install of RAM Doubler as a possible solution.