Hi everyone,
I'm hoping someone can help me with this issue I'm having with my G53SX. By the way, I work in IT, so please, get technical with me, I'll understand.

The problem I'm running into is similar, but not exactly the same problem as the Black Screen issue, which is the issue where the screen stays dark but the system finishes the Power On Self Test and boots windows without display.

My problem is different. When I power on the laptop, it does power on, but it will not finish the POST sequence. I can hear the system fans turn on, and I hear both the DVD and the Hard Disk initialize, but the keyboard does not light up, the system fans do not do that signature max-out when the BIOS fully POST's, it just sits there.

I already sent it in to Asus for service. (Case # USG9291764) and they sent back the form stating
Issue was Duplicated. Your laptop has been Repaired.
No specific boxes were checked though, and no specific entry was written in the Other box.
They DID re-load the OS because I sent the laptop in with the hard drive blanked out. They restored the factory software. I recieved it, and it worked great for a day. The next morning, I turn it on only to find that it's doing the same thing. It refuses to finish POST when powered on.

I have tried removing the battery and running just off of the AC adaptor. Same result
I have tried another known good battery (I have two of these laptops, exact same make and model) Same result.
I have tried another known-good AC Adaptor, same as above, same result.

After trying the usual, and poking around the forums and Asus's support site, I found an article mentioning to check the RAM. So I did that, I disassembled the laptop and removed the RAM chip from the user-accessible area where you take out the cover to get to the hard disk.

Things got strange after that. I tried powering on the system, just having the one RAM chip that's installed underneath the keyboard and powered on the system. The system still refused to POST, but it would automatically shut off, then power on again. It would power off and on in a loop, 5 seconds on, 5 seconds off. I pulled the AC Adaptor and battery, tried with each power source individually, same results.

I dug a little deeper and removed the RAM from the slot underneath the keyboard tray (got lucky and did some tricky work with two plastic spudgers to pull the retention clips apart holding the RAM stick in place.) and put both RAM sticks in the user accessible area next to the hard disk tray. I then powered on the system, and it POST'ed! It actually worked. I then ran Memtest86 on it for a little bit and noticed it was in Single Channel mode. So I moved the stick that was underneath the keyboard, to the user-accessible slot underneath the keyboard tray to put the RAM into Dual Channel mode. Essentially now, slots 2 and 4 are occupied with the original system RAM.

I powered the system on again and ran Memtest86 overnight. It completed over four complete passes and threw zero warnings. I booted it up into Windows, and ran Prime95 on it for an hour to see if temperatures would hold steady - they did. I also ran a couple of 15min Burn-In tests using FurMark. (These benchmarking tools were recommended in finding out if the system is affected by the 700MHZ downclock issue, this system does suffer from this problem, and running ThrottleStop as recommended in the sticky post does fix this issue.) So, it worked normally in some benchmarks in Windows. No crashing, no bluescreens. It worked for one day, then it started in AGAIN with the no-POST problem I had before!

So at this point, I understand why the Asus service center sent it back with nothing checked on the paper - obviously when they received it, it must have powered on for them normally, like it did for me after I re-seated the RAM. So - I'm not sure what to do at this point. I've tested the RAM, yet the machine still goes back into the no-post issue. I'm afraid if I send it back in to Asus, it will operate normally, and nothing will be done to the laptop again.

//Knock on wood
My other G53SX has never exhibited any of these issues (except for the throttle issue which is beyond the scope of this thread) and is still running well.

Does anyone have any suggestions, perhaps anyone I can contact at Asus rather than calling the support number to submit another request? I would suspect it is a motherboard/RAM slot issue at this point, and would request that the Motherboard be replaced... it's difficult though because it's an intermittent problem, and I would really like to resolve this issue, because after getting past the throttling problem, it works very well.