Hello [NAME], The QLogic 57840 QP 10G KR is endeed supported by the PowerEdge M640 and more specifically, the part number XV66X is compatible with the PowerEdge M640. The CMC firmware version 4.4 was the one that introduced the Broadcom 57840S-k Quad Port 10GbE Blade KR NDC compatibility. Can you make sure the firmware baseline is updated? (not only CMC, but all components) I think the problem of the Power Edge-M IO modules guide is that the revision date is from April 2013, so it is not fully updated. Regards.
QLogic 57840S 10Gb Quad Port KR CNA bNDC Blade m620 bNDC part number JNK9N runing fine on M1000e chassis. Adding new M640 blades with "QLogic 57840S 10Gb Quad Port KR CNA bNDC" part number XV66X looks like up an connected to force10 MXL on fabric A when looking to port status on MXL switches but no traffic there. Referring to Power Edge-M IO modules guide, it doesn't mention quad port 57840S-k with G14 blades! but it mentions that it is compatible with MXL. Dell website customization product shows that this bNDC is for M640. M640 can see this bNDC and configure them and booted successfully. to sum up question, is it valid configuration to use: M640 with QLogic 57840S 10Gb Quad Port KR CNA bNDC" part number XV66X  on M1000e midplane 1.1, IO module type is 10 GbE KR using Force10 MXL 10/40GbE on A1/A2.  
quad port 57840S-k bNDC on M640 compatiblity