over the last few years i have encountered several sts ksus locking up. display comes up but with no sync message. default sometimes helps but some just wont come back up. my question is does this mean it is a software problem and the rest of the ksu is good. thanks dave

My experience has been that this is caused by one of two things...power supply going bad (-5 volts) or the ram battery is starting to fail.
It is easy to test the battery. Take a meter to it and make sure it has over 3 volts when the power is off. There is no test for the -5 volts. When it goes the unit will start clicking like crazy.