Which software have you tried for burning the firmware, and what version?
From memory (it's been a long time), you'll need to use "flint" prior to the 3.x.x releases. eg 2.7.2 should work:
http://www.mellanox.com/downloads/MFT/mstflint_x64_2_7_2.zip
Other flint versions should be downloadable here, if I chose the wrong one for that link: Mellanox Technologies
It may be better to use the verion of flint (mstflint?) that's packages in RHEL 6. I don't have a box handy to check it on right atm.
Guessing you've figured out how to retrieve the model number and revision of the cards? It's in the output of lspci above. Be sure to double check each card individually. I've had different revision numbers of the same card happen in the same batch (needed different firmware). No idea if that's common though.