please help me finding out the isuue with my rig

In dire need of help.....
My Rig cofig-1)PSU CORSAIR GS800
2)MOTHERBOARD MSI P67GD65
3)GRAPHICS CARD ASUS GTX 560 Ti DCII
4)RAM RIPJAW 1333 MHZ
5)COOLER MASTER CM STORM CABINET
6) AFTER MARKET COOLER
COOLER MASTER HYPER EVDO.
7) UPS APC 1100 VA

That much is enough I guess for the solution I need.
My rig was fine,it was working like a charm with no issue in it bt fr the last 2 months almost I m facing a difficult prob with my rig. My PSU is keep on getting dead every time I replace it with a new PSU given by Corsair as a replacement.Including it every equipment of my rig is covered with warranty except my mother board which had got some physical damage during transport.I repaired it frm MSI service centers itself by paying money becos the damage was physical not covered in MSI warrenty.corsair has already given me two times new replacement of GS800...though m nt sure its dead or not bt every time after using the rig for 2-3 days with new PSU when I usually go to start the rig its simply doesn't start.initially I thought it may be a prob with my earthing becos I never had proper earthing on my house so I done it and after that I replaced my PSU bt no change,same prob,now one other prob it can be, what m thinking,I usually have over voltage prob in my area where I live, we usually get 260-265 volt at evening where the rated PSU max vaoltage is 240 volt(nt used UPS). it may be a reason what I am thinking though m not sure.recently corsair service center after giving 2 times replacement they are telling that I am having prob with my motherboard,so they are suggesting me to contact the MSI on this.

My question if I got any issue with my mother board how the rig works fine fr even two days every time I replce it with a brand new PSU?
If its nt the prob with MB why the rig dosn't starts after 2-3 days of usage with new PSU or PSU gets dead every time?is it the prob with my volatage?
I m right now residing frm a small urban area in India...so nt much of help frm professional is available here...Thats makes me write all this on this blog....any help from anyone will be very appriciated....need any more info pls write will give every bit of it....thanks in advance.