The problem is that you actually have less memory
available when you
run XM since it is a larger monitor. And we're talking about memory
in the critical area of the low 56kb.
If VGBEXE is no solution to run ADVENT, try using the SJ monitor.
I had exactly the same problem (in E11) and lots of memory available.
Booting into SingleJob was the solution for me.
Didn't help much getting throught ADVENT, but that a completely
different story ...
happy gaming,
- Henk.