Hardware PS3 Strange Power Off issue

[twig123]

My Fat 80gb unit YLOD'd and I reflowed it (believe the 3rd time now). It is no longer having a problem with YLOD, but has another strange power problem.
I can mess around on the PS3 menu or multiman for a long time and have not had an issue. I start any game and it will load to the start screen, I press whatever button to actually start playing and the system just powers off to a solid red light (no beeps). It acts kind of like someone flicking the power switch off then on again.

Ex: I start LBP, it loads and I can run my character around my pod... I select a level and press x to start, and the system powers off.
This is the same with LBP2, Sonic Generations, Dead Nation PSN, Army of Two... all do the same thing.

Thoughts?

Edit: Doesn't matter how long the system is on, it happens anytime I try to play a game. I tested by leaving the system off overnight powering it in and directly launching LBP from disc, as soon as I select the level *poof!* it shuts off. Really strange... I'm currently reflowing the system again in hopes that it will fix the issue. I'll report back with my findings.

 

[twig123]

Hmm, reflowed again and still the same thing.
As a last ditch effort I took out the copper shims I had, and all works fine again!

Very strange! Not sure why shims would cause this problem... but oh well.