It sounds like something isn't ready (maybe network connections) on the machine when it tries to start. If it behaves differently between a cold boot and a hot reboot, then it can't really be a bug in MC, something on your PC is acting differently between the two.
Just to be clear, when you shut down and then boot back up, MC launches in Theater View as you'd like, but nothing plays (not the wrong thing plays). Right?
In any case, this should be easily solved by scheduling a MCC command to play Playing Now in the Windows Task Scheduler.
Start > Type "Task Scheduler" and hit return on the Task Scheduler to open it.
Make a new Basic Task.
Give it a name like (MC Starts Playing)
Under Trigger choose When I log on.
Under Action choose Start a Program, and then paste this in:
Program: mc18.exe
Arguments: /MCC 10001,0
Choose Open the Properties dialog for this task when I click Finish.
In the Properties dialog, switch to the Triggers tab, and Edit the trigger.
Check the Add a delay box, and set some kind of delay (hint: you can type whatever you want in the box, or pick from the presets).
Keep MC set to auto-launch on boot, as you had it. This will send the Play command (which will play playing now) when you boot, a few seconds after login.