Having Y.L.O.D. Repeated Problems

I was wondering If someone could help me with this problem. Recently I got the ylod on my PS3, and I ordered the ylod fix kit from this site, and I used It and was successful with repairing the PS3. The PS3 worked for about 2 weeks then when I was playing Dead Nation the game froze about 10 minutes In and the system shut off and beeped. I then turned the system on the next day and played Wipeout HD, and the system did the same thing, froze 10 minutes In, turned off and beeped. The next time I tried powering the system on I would just get the ylod. So I took apart my PS3 again today, and cleaned out the fan, the casing, etc. and put it back together and It still has the ylod. I was wondering If anyone else knew of any other problems that could be causing this, because when i try powering It on the fan turns on for a second and then the quick ylod comes and beeps. Thanks for reading this and thanks for any advice.