|"...the monitor keeps flashing from analog to digital .."|
That's probably not what the led colors indicate.
If your monitor can only be connected via a VGA connection or a DVI connection, and not either one, one at a time, (a few monitors are both DVI and VGA) the led color either indicates the monitor is getting a video signal - usually when green - or it isn't - usually when yellow or orange - NOT that it's in analog or digital mode - most monitors are either analog or digital.
Your system being relatively recent doesn't necessarily mean it doesn't have accumulated mung (dust, lint, etc.) on the cpu fan and heatsink, especially if you're running it 24/7, or if you also have case fans. The more time the computer is running, the more fans you have, the more dust and lint that can be sucked in, the faster the mung will accumulate.
E.g. A friend of mine who has a 6400+ cpu and a case fan, one power supply fan, has wall to wall carpet and his cpu fan and heatsink have to be cleaned about every three months because of accumulated fuzz from the carpet - no one in the household smokes, and the computer is a long way from the kitchen.
Whether a power supply boots a mboard all the way depends on a signal "power good" being generated by the properly working mboard during the POST.
Whether a power supply shuts down a mboard depends on software in the operating sysatem generating a signal to the mboard - if the operating system is completely frozen , it can't shut down the mboard, and neither can the Reset switch on thecase if it has one.
In most cases, the default settings in the bios setup for the mboard will shut down the mboard when you hold the power button in for at least 4 seconds.
I know very little about Linux.
Apparently kernel panic is the same situation that causes blue screens of death in Windows - the operating system experienced a fatal error it can't recover from.
Apparently you often also get a message about what the problem is when you get a kernel panic error, the same as you usually get a message along with the BSOD in Windows.
If you quoted that other message it may give us clues as to what is going on.
If you are experiecing cpu overheating, all sorts of bizzare symptoms can happen, but they usually only happen once the cpu gets above a certain temperature - they don't happen when the cpu is cooler than that.
Unplug the case/power supply.
Power off your monitor.
Open up the case by removing the left panel as seen when you're looking at the front of the case.
Check all the connections of the wiring to make sure they are all the way onto their pins and into their sockets, especially the main connector from the power supply. The wires close to the mboard going into the main power connector/socket should be more or less perpendicular to the mboard surface rather than at an angle. Make sure all cards in slots are all the way down in their slots.
While you're in there, if the cpu fan/heatsink has mung (dust, lint, etc.) on it, clean it off, but DO NOT use a vaccuum cleaner to do that (they produce a tremendous amount of static electricity when running, and anything connected to them can discharge that to your components) - use canned air, or an air nozzle if you have access to an air compressor, or an artist's brush that can be used in small spaces, etc. It may be difficult to clean the top of the heatsink under the cpu fan - the most likely place to have mung on it - and the bottom side of the cpu fan blades unless you remove the fan. If you have a case fan, clean that too if it needs it.
With the cover still off, restore the AC power, start the computer and make sure the cpu fan spins - if it doesn't spin, if you're sure the power supply is working okay, don't use the computer until you have replaced it.
If it spins too slowly, and/or if it makes rattling or screeching noises, most likely to be noticed when the computer has cooled to room temp, has not been used for a while, and then is started up, the cpu fan's bearings are failing - replace it as soon as you can.
See response 2 in this - try cleaning the contacts on the ram modules, and making sure the modules are properly seated:
Do the same thing for the video cards, and any other cards you have in slots."
If that doesn't help, try another power supply, 400 watts or more capacity.