This article is from the Amiga CD32 FAQ, by Stuart Tomlinson with numerous contributions by others.
A: If your CD drive uses the PCMICA slot, you've got a RAM board in the trapdoor slot, it's got more than 4 meg of fast RAM, and it doesn't Autoconfig properly, then the drive may refuse to work or you could lose all memory above the 4 meg barrier because the PCMCIA slot and the memory both try to use the same address space. You could only use 4 meg or you could ask your dealer for an upgrade.
Some trapdoor accelerators don't Autoconfig properly either. Notably Amitek, Blizzard, and GVP ones. Amitek offer a free upgrade to fix this problem. The Blizzard 1230III and the GVP 1230 '030 boards work fine, don't know about other Blizzard and GVP boards. All of the Microbotics boards work.
If your CD drive uses the trapdoor slot then you can kiss goodbye to RAM expansions and accelerators.