What type of equipment are you connecting to the ports? DCE equipment will use a straight-through cable. DTE equipment must use a cross-over cable. (Called a null modem cable.) Check the specs (pins) for your equipment. Also check if Hardware Flow Control is turned on for the COM ports. If it is, the equipment must raise CTS and/or DSR to receive data.
Forgot to Mention: Make sure the COM ports are turned on in the BIOS.
We are connecting it to a piece of equipment that we manufacture ourselves. The equipment communicates fine via a virtual COM port provided by a proflific USB-to-RS232 adapter (both on the D510MO board and on other PCs) as well as communicating with physical COM ports on other PCs with the same 9600-8-N-1 settings.
Everything is the same (same D510MO board, same piece of other equippment, same RS232 cable) - The only thing being introduced outside of that is the three inch cable, wired as above, that goes from the COM header on the D510MO to an RS232 connector and this is the only scenario where to doesn't work.
I normally look at this unit via VNC, so it would take some moving around to get a keyboard/monitor/mouse hooked up to it to look at the BIOS - so I wanted to ask before I do that: could the COM ports be turned off in BIOS and still show up in the W7 Device Manager as working properly?