I had way to many problems recently with my 360, but since my warranty is voided (chipped xbox), I had to repair it myself...
I first fixed a RROD by doing the penny trick wich worked perfectly (youtube it)... After this, my 360 got a new problem, everytime my xbox runned for more than 5 MINUTES, the screen would freeze with white shaking lines...
I solved this myslef by removing the center screws inside the xbox... Wich made a bit more space for the xbox to "breathe"... After thoses 2 solved, I got the 2 red lights of death... Tired, I had to re-open my xbox again...
After some research I found that it was also a overheating problem... So I changed the glue that microsoft had put on the ram chips (where I glued the pennies to fix the RROD, but I did'nt add any glue at that time, used the one thats was already in the xbox)... I removed the original glue to put some regular glue (with a heatgun) under the duct-tapped pennies...
1 months and half as passed and still no problems yet! Hope I helped someone.