PC reboot on heavy loads (PSU problems?)

[RicardoBR]

Hey Guys!

My PC is rebooting when doing tasks that stress both the cpu and gpu (when i stress them separately everything is fine). The problem started a few days ago and i can't figure out if  my psu is dying or not.

 

Windows 7 x64 ultimate 
fx-8320 @4.2 cooled by seidon 120v WC(i also tested @3.2ghz with no luck)

ga-970a-ds3p bios f6j
16gb ddr3 hyperx fury 1600mhz (x4)
r9 280 ASUS DCUII

PSU: Zalman dual-forward power suply 700w zm700-glx

kingston ssd 120g and 2 seagate HD
 

Any help would be nice! Thanks and sorry for my bad english

[TerminalVelocity]

Do you know the wattage of all your parts are?

[RicardoBR]

Psu calculator gives me a minimum of 520w

[RicardoBR]

Hey guys any news?