Hi,
This has intrigued me as well.
I have a MKII Blizzard 030/50 and have used it with a Sqirrel (SCSI) CD ROM no problem.
However, why the external PCMCIA Drive should clash with your memory is baffling ?
My only suggestions are, double check that you have the Memory Jumper Settings correct on the Blizzard, and also, check to see if the Blizzard has a SCSI Card attached.
Edit.
Perhaps you need to install some software to enable the CD ROM to be seen.
Regards, Michael
aka rockape