This is an out-of-memory error. When using three or more monitors, you
need to ensure that the applications have enough memory to support three
screens worth of data and word processing cut, copy, and paste functions.
If you use MultiFinder or System 7, you need to increase the amount of
memory for each application. If you run on a 1MB system, you need to
remove anything that uses extra memory. You should also switch to the
lowest bits/pixel possible (two).
(NOTE: The LaserView in particular uses a lot of system memory when it is
running in "high" mode. This, coupled with using two additional monitors,
may be the root of the problem.)