My guess is that McAfee is hitting up against the 640k - 1MB memory range that all programs require a piece of to launch in all of the Windows 9x platforms.

Manually try setting your script to run from either a startup group, or the RUN key in the Registry and see if it works. If so, then I would guess it is the memory problem. i.e. something is either fragmented in this memory range or something is stealing too large of a footprint of this memory and won't share it.

Let us know how it goes.

Also, welcome to the board.

By kixtart it is possible to create a new DOS box (= vdm) to run an
application. Memory management will be good in such situation.
We have never modify for Windows 9x/NT/W2K memory management part.
We are using always the default configuration for it.

How to create a new DOS box by running kixtart?

SHELL '%comspec% /c your_application.exe'

by using SHELL 'your_application.exe' you are running in current
environment space. same space were kix32.exe is running.

Greetings.