Did you get these from ebay? Because if you did I'm screwed...
i received them from ebay seller ynlcabin8,i already received full refund.
i also received same risers from another seller and all fine.
What kind of graphics card did you attach it to?
Did you forget to attach the PCI-E power cables to the graphics card?
msi R5850 ,no i didnt forget to attach pci-e power cables
PS seller said that he know about problem,so it was low quality riser
What PSU are you using?
it is used for 3 months with that 2 cards w/o risers,so i m sure that PSU is fine,problem was with riser
PS there were no problem with x1-x16 risers ,simply connected and it works