I have had similar problems when changing from Blu-Ray to DVD and back.
What I did is remove the disk and power the unit off. Then I power the unit up by hitting the tray button instead of the power button. When I pop in the disk and close the tray the player has a better chance of recognizing the type change by having the different disk in there while it is booting up.
I also have the latest firmware and run into strange problems where the player ignores the front panel buttons and / or the remote. Doing the above seems to cure the problem.
I have also been told that holding the FF button for 11 seconds forces a reset. I have not tried this yet.
My BD-P1500 has worked great for 7 months until today. It stopped being able to read DVDs and CDs. It still reads Blu-Ray discs. Here's what I tried to resolve the problem:
I upgraded the firmware to version 2.4 via USB
I did a factory reset
I unplugged it for an hour
I ran out and bought a 25' ethernet cable so I could try updating it that way.
I did a live chat with a Samsung service tech who went through all of this again, and he verified I had the latest firmware. He told me to fill out a service request.
I filled out the long service request, only to have it tell me I couldn't use the form and needed to call the technical service number.
Called the number and they were closed for the day.
This is really frustrating. The parts should still be under warranty, but it's almost definitely going to have to cost money for labor to fix it. It seems like many others have had the same problem and I don't think I'd recommend a Samsung player anymore. Has anyone else out there been able to fix it without sending it in for service?