Just updated from Ch 2020 which was working fine. The spalsh screen freezes on
Initializing (Loading TransmitFullScreen.prm)
Update: Same issue now with both 3.5 and 4.0, after uninstalling/reinstalling both.
The issue in my case was Mediafoundation.dll attempting load codecs from a mapped network drive that was offline. Bringing the drive back online resolved the issue.