x86 and NIC cards

We recently purchased a HP server with 2 internal Broadcom 1Gbit interfaces. We tried installing two additional Trendnet TEG-ECTX cards. Only one of the new cards shows up in RouterOS. Is there a limitation on the number of active interfaces ? If not any ideas how to get the second add on card to be usable ?

Thanks in advance

http://wiki.mikrotik.com/wiki/Supported_Hardware