If I switch from Morrowind (which is running in fullscreen) to another window by using alt+tab, and switch back by using alt+tab, it seems to work as expected.
However, if I switch to another window, then click on the Morrowind window in the taskbar, it will crash every time.
That is all the information I can provide at this time.
Actually, I've noticed that the game sometimes crashes when only using alt+tab, but not every time.
I am using Morrowind 1.6.1820, MGE 3.8.0, MSWE 0.9.4, on Windows 7 32-bit.