I know this is not what you guys who have an M5G or an M5F that seems to be faulty want to hear but my M5G and M5F have never let me down. This is despite, since having an M5G and M5F from when they first became available in the UK. In my M5G I have swapped an Antec 920 for H100, two case swap rebuilds, a twin 570 GTX in SLI swap for a GTX560ti an i7 2660K for an i52550K swap and all this on the first release BIOS. I had seen the A2 error posted on the forum about this the M5G before and more recently about the M5F a few times so out of curiosity I set out to see if I could force this error and then fix it, mad I know but I have few systems up and running so I can play around as that is how you learn stuff with computers, try and see!
I have managed to replicate the A2 error deliberately now a number of times and fix it on both my M5 boards. It seems to me, based on my own observation, always to happen after disconnecting various hardware and then not refitting it properly, i.e. cable for SATA, GPU card, PSU 8 pin CPU and/or RAM sticks. I have deliberately then refitted these various components sloppily and by this I mean not fully fitting or snugly fitting a cable or component although they seem to be in the various sockets etc. The board is very unforgiving with these sorts of problems so my advice would be to persevere and try the good advice you get from the fantastic guys on this forum. Given that a lot of people praise this board I think it is unlikely that everyone who has a fault with their M5G actually has one that can only be resolved by RMA; although I do think that statically ASUS will have a small number of faulty boards in commercial circulation as the cost of 100% quality compliance is almost certainly to high in terms of production overheard cost and quality. A fact of the balance between modern engineering production and the profit margins. However, this said I am sorry but I just don't think the ASUS manufacturing process or quality control process can be that bad? I say this based on use and quantity! I have four ASUS boards all running at the moment in fully built up systems ( M4E, M4G-GEN3, M5G and M5F) based around commercially purchased main stream boards from SCAN UK and all working without faults and used regularly by members of my family. The M5G and M4E get hammered by my own children and teenage grandchildren who game on them at every possible opportunity, work and school work allowing. I know my comments may not be popular but that is my opinion but I do accept that others may disagree.
If this post is inappropriate or in the wrong place then I am sure a moderator will take it down.