Confusion over SFP+ module compatibility

Hi all

I have the following configuration that i'm trying to get working

Server with a Broadcom/Qlogic BCM57711 Dual port NIC connected to a Dell Powerconnect 6224 switch with 2x 10GB XFP module addon

Switch has the following module installed:
Dell FTLX8511D3-FC 10Gbps XFP Transceiver GP-XFP-1S 02C4K7

I used the following module in the server end:
Cisco SFP-10G-SR

I'm using an Orange (I think OM2) multi mode fiber patch lead

The port on the server doesn't come up - it has windows installed and it's not disabled or anything stupid like that.

I know the modules at both ends are OK because if I put the Cisco 10GB module into a Cisco Nexus 5020 switch, and connect that to the Dell switch, it works!

And the server NIC is also OK, because if I connect a DAC cable between it and the Cisco Nexus, that also works. It's just this particular setup with the Dell switch that doesn.t

Should the Cisco SFP+ module not work in my network card? I can't find any info online that says if it should/shouldn't

Thanks in advance