Hello Mike,
We have had several Microsoft updates causing trouble for us lately, so I just updated my computer to verify that that wasn't to blame for the issue you're seeing. I'm all updated and able to load Mach4 without issue. The most common culprit is AV software. Are you sure that Bitdefender is completely disabled when you are using Mach4? You also mentioned running as administrator, which is something you definitely want to do. To clarify what I mean by "running as administrator," you should right-click the shortcut you use to open Mach4, go to Properties, Advanced, and select 'Run as Administrator.'
A fresh install might be a good idea as well. Make sure Bitdefender is disabled (I am not anti-Bitdefender by any means, but it is known to cause a world of headaches when used with Mach4) and reinstall. If that has no effect than we will keep digging.
Thank you,
Bryanna