The same thing happened to me.
At first, my Xbox 360 would randomly freeze up.
I had to get up out of my seat and manually turn the Xbox off and then back on.
Then the freezing got worse and worse. It reached the point where I could play for only about 5 minutes before it froze again.
Finally, it got to where the red triangle of death appeared as soon as I pressed the power button.
I couldn't even access the Xbox 360 Dashboard.
Fortunately, my 360 was/still is under warranty and I sent it in.
Seems you & I aren't the only ones who've had this problem.
When I took it to the UPS Store to send it to Microsoft, the guy there told me that he ships 10-15 broken Xbox's to the Microsoft Repair Center every week.
And that's just from people in my town!
I cannot begin to imagine how much Microsoft has spent on this problem so far.
When I got it back about 2 weeks later, there was a pre-printed note in the box which stated that they had replaced my old console with a new one.
And they gave me a free 1 month Xbox Live time card for my trouble!
Since your warranty is probably no longer valid, I recommend paying the $140.
That's a heckuva lot cheaper than buying a new system.
By the way, what's your Gamertag BlackAngel?
Feel free to add me to your friends list.
My Gamertag is ASHTHECAT3