Faulty RAM?

Guys,

I would really appreciate your help as I am having a nightmare!

I bought my PC a few years ago from Overclockers as one of the overclocked models (Think it was a Ultima OC 8800GTS, I still have the receipt if this info is needed). It's been an excellent machine and with an updated Graphics card still runs everything fine. It's got 4gb (2 x dual channel) Crucial Ballistix RAM and a Q6600 quad @ 3.2ghz on a IP35 Pro motherboard. The RAM was also overclocked by Overclockers and I still have the settings.

I changed my Graphics card to a Palit GTX OC 460 in September and shortly after started having problems - The PC will boot (Works fine in windows once booted) but it only boots intermittently, as I changed my graphics card around that time I assumed it was this but have since tried it in my brothers machine and it works fine in that. However I did replace the PSU to an Antec 650w as originally I thought it was the PSU.

The post codes after booting are C1 and 0D - After Googling these appear to be the RAM although I have ran Memtest and everything passed fine. I have tried booting with a single stick of RAM and the other 3 unplugged but the PC still only boots intermittently. I took the battery out yesterday and will try again tomorrow as I don't have time to mess around today.

Questions I have are:
1) Should I try increasing the Ram voltage to 2.3v? From memory it's currently set as 2.2v and has ran fine for years, is this safe to do? From reading on Google it appears as memory ages it may need a higher voltage?
2) Is it even possible that all 4 sticks of RAM could get damaged at the same time?
3) Do you have any other suggestions?
4) Another question would be how long can a PC like this last that has been overclocked for over 3 years? I know no one can really tell me but should I be thinking of selling up and starting again or do you think it will be fine for another couple of years? If this is suggested I would like to get this PC working fine so that I can sell it for funds to put towards another one. However I don't really need any extra power/RAM as it still runs everything I need it to (It seems after I bought this system the PC power increases have slowed down considerably, good timing for me!).

I would also mention that when I bought my PC I also bought another identicle PC for my brother and last May we had to replace 2 of his 4 sticks of Ram as they were faulty. I e-mailed the manufacturer (Crucial) at that time who advised the original RAM in my brothers machine was no longer produced and advised an alternative updated version with the same specs of BL2KIT12864AA106A. We bought this and his PC has been fine since (Apart from having to replace the PSU when that blew up in August time).

Thanks for all of your help, it is much appreciated!