Outright failure is a no brainer. Recently I had an OS100R2 with expansion, MGI3, SVMi-4,3 - 6Trk, 2 - 8DLI. Everything worked EXCEPT the com port on the SVMi-4! 5VDC measured 4.95. I got crap on my screen. Long story short - power supply. In loaded systems like this make sure it is the new design power supply from Samsung with large caps (size of 1/2 dollars) and 6 small switching transistors. Forewarned is forearmed.

Once a power supply starts to fail it will do strange things.I had one that would randomly reset the system.It was a sign that it was on it's way out and couldn't handle the power requirements anymore.

MANY people do the repair on these units, NOT just the "authorized" Samsung dealers.

Got a 500 PSUB power supply fixed by our Sundance hosts (www.usedphones.com) for $80 (includes a $20 promotional discount), just try getting a deal like that from the "authorized dealers"