Intermittent Computer Problems

hi:
 
Sonar works fine most of the time.
Every now and then it does strange things.
 
Sometimes it will shut down by itself; Completely off.  Other times it will
reboot itself to the signin screen. (I only use Sonar with this machine so
that is the only application I run (so I don't know if it this problem is particular to Sonar or not)
 
Other times, it will not boot up to the sign in screen; The computer is on, but just a blank screen.  I have switched moniters (it's not the moniter)
I have replaced the video card (NVidia) Same thing with both cards.
 
My Ram checks out ok...
 
I'm not sure about my power supply; It should be enough to run my
system but I do have a lot of USB plug ins (external hard drives, etc)
 
I do use a firewire Sound card and I do not have a Texas Instrument Chip set in the computer.
 
but like I said the computer runs fine most of the time.  Just annoying shut downs a few times a week.....
 
Any suggestions?  I do have a USB sound card I can use to replace my firwire card.
 
By the way, the system ran great for about a year;  and seems the problems started after I updated all the drivers...
 
I use my system for business so I am not connected to the internet;
When I finally did connect after a year or so I was way behind in updating my ststem, if that helps.
 
Vista 64 bit OS  Sonar 7

thanks Bill
 
I mispoke on a few things;
 
First my Ram has not been checked (I thought my partner did)
but I did reseat the ram, and since then no problems.
 
Does the problem I have described sound like a Ram problemo?
 
If a desktop is running too hot, will it shut itself down?
Will there be a message before?  Will it reboot?
 
It has been a few days since the reseating of Ram and so far the
computer and Sonar are working fine.
 
the next time it happens I will check the system event log

I agree...
RAM would be the first thing I'd check.
You can download a free CPU temp monitoring app (or have a look in the system's BIOS).
 
BTW, The FA-101 is one of the least finicky Firewire audio interfaces when using non-TI chipset Firewire controllers.
It's very forgiving...
That said, similar symptoms could indeed be the result of using a Firewire controller that's not 100% compatible with your audio interface.  Using TI greatly reduces the odds of having a problem.  If you're dealing with a desktop, I'd get a good PCI or PCIe TI chipset Firewire controller... and be done with it.  You'll never have to wonder/worry... (~$30-$50)

thanks for the responses.
 
The computer has been stable for the last week or so.
 
Thanks Jim
I have on order a PCIe TI chipset Firewire controller;
 
I'm also going to upgrade my PS; (it's cheap enough even though it may
be overkill)