The place I worked at awhile back brought a bunch of new ProStars in 2009 and got rid of all of them within 2 years. All of them had electrical and computer issues. 

Derates occur after extended idle or low load periods when the DPF becomes loaded to a point needing regen, many of these filters require a Periodic REPLACEMENT with a repair service regenerated unit as the onboard systems cannot fully clean them.  The Western Star I routinely drive has 294,xxx miles and has had this performed now once, the freightliner I also run is at 125,xxx and is due for the procedure, BOTH have DD13 Detroit Diesels in them.  Heavy machines the company owns with the systems warn the operator a Regen is about to occur where they can get to a sideline position to allow the machine to do its business, takes about fifteen minutes, where most of the trucks require a fifteen minute idle period before shutdown to allow the calibration system in the processor to evaluate the emissions system.

A few years ago I was having trouble with my 97 Freighliner with a Cat 3126 engine.  Got to the point I wasn't dependable to drive.  Took it to an independent dealer, who finally diagnosed it as a faulty main engine computer.  One of the mechanics there mentioned he heard of an outfit that can reprogram the computer, don't remember the exact cost but it was less then $2,000 including overnight shipping both ways. When it came back, the shop manager told me it would be like a new truck.  He was right.  I asked how he knew it would be so much better.  He told me he got a call from the outfit in Texas that did the reprogram, the person asked if this was a truck or a gen set as it was set up for a Gen set.  The reman engine must have been set up for a generator and nobody noticed that when they put it in the truck.

I don't know the name of the outfit in Texas but I'm sure some time on the internet would find it.  Might be a lot cheaper then a new computer.