Wow, thanks for doing all of this testing, that's great info .
When you do test the beta, please set McAfee back to High Priority (default) and see if it's necessary to change it to avoid the problem.
If that doesn't work then simply exclude McAfee's Program Files folder from MBAM by using the Add button on the Ignore List tab (a new feature available in 1.50). Just make sure it's the folder that contains McShield.
Once that's done, reboot and see how performance is and if you can scan with McAfee.
No problem Exile. If I can get my clients with McAfee set up and running with a license for MBAM it's going to be a big help for me and also for them. I'm happy to share that info here so that others can also benefit.
I will try your suggestions and post my results with the beta.
So far its looking to me that McAfee/MBAM conflicts seem to fall in to two categories:
1) The problem of setting proper exclusions. (workaround= creating the registry values for exclusions manually)
2) McAfee hogging too many resources on older systems. (workaround = Lowering Priority?)