Long story on this one, roots in the fact that I have ACP7 on my dev machine and I needed to get an "oops" release of Scheduler out... Anyway, the 3.5.3 installer left a copy of ACP.exe in the scheduler folder. If someone starts it, things go bad. It can be easily "fixed" by starting the correct ACP.exe.
Need 3.5.3a installer with that problem fixed.