MPC 4000 wont load past start up

got the same problem sometimes also.i went back to os 1.60 and mostly solved the problem!!!!!!!also hooked up a multi output board and same thing,dosent boot properly.LOOK in this state the pc prob will not recognise the mpc SOOO turn on the machine with window shift buttons pressed together and youl have a page thet prob say os invalid!!but now your pc can recognise mpc and you can flash your rom.1.6 is on akai website.yeah and check your ram...

NOTE-only use shift window as a last resort as you will have to load your os again.

I am having the same issue where i turn on the MPC4000 and get stuck on the start up screen. PLEASE, if anyone has a fix, let me know.

I am using OS 1.71. When I attempt to use OS Loader to Load the latest or prior OS version I receive an error that my computer cannot recognize an external UBS device. I also tried to hold down "Main + Shift" at start up. Neither worked.

^^^ Won't work if you haven't installed the USB drivers on the computer first. Once they're on there and you connect the 4k, your comp os will reconise it and you're good from there.

Thanks for the tip. I tried a Mac G4 so I don't think the driver is the issue. I'll try a PC next after having installed the driver.