If the buttons are just sticking at their sides in the panel, lube with a tiny bit of CRC 226 on a Q tip. Get the CRC226 at Home Depot in the electrical dept. If the button mechanisms have failed or plastic hinges have broken then replacement is only option. Losing 4 of these to same problem is RIDICULOUS... time to change brands.
do you have the owner's manual if not download it-there are /were you tube videos for what your trying to do- they helped me alot - when you plug your guitar into the guitar jack on channel 1 you can't use the xlr input 1at the same time in addition be careful not to blow the audio system there are no replacement parts for this system
Korg is a great company and when you contact them they will help you. They can tell you how to get the CD and/or how to download and burn it to your own CD. then you can boot up the device
Somehow proper save and shutdown was not done. You said the magic word PANIC... That is a deadly word in this situation. So first thing like for lost files on a PC is to look around... carefully. LIKELY the files are still there, just under a different folder or imbeded in another project. These systems do a pretty good job of not letting one clobber their files without confirming AS LONG AS proper shutdown procedure is used or power doesn't fail. The five tracks you might have forgotten to save...but the other should be there.
Unless you are electronically adept and have certain tools I would NOT attempt this yourself. You could damage the circuit board causing great repair expense.
Here is a link to the manual:http://img3.musiciansfriend.com/dbase/pdf/man/m_242061.pdf Just remember the mentioned site has lots of support for other brands too.