Find another GA-Z68MA motherboard on Ebay and replace the one you've got. I'm still using the exact same mobo right now and it has a lot of life left in it. Make sure the BIOS of the one you buy is the same as your previous one. If not, perform a BIOS flash.
I bought mine in Jan. of 2012 and it's been used daily ever since then. I do clean the dust out regularly, keep it cool and take very good care of it.