Thanks, Gilles! I was beginning to suspect romless, too, but my attempts to use a ROM (on Mac, anyway) were greeted with the same IPC error.
EDIT: Apparently, this is a two-step process. If the ROM is split into hi and lo, and you select bootrom.hi in the Preferences menu and attempt to boot, ROMless mode will still be used *until* LisaEm has joined the hi/lo ROM files into a single boot.ROM. I seem to recall this happening automatically upon closing Prefs, but it's inconsistent now. You can attempt to boot and get presented with the "ROMless Boot" window, then hit cancel. The ROM files will be joined, then subsequent boot successful