Double check to be sure the ports you mapped in your router are in mIRC's options under dcc/options (where you see the default of 1024-5000) It might also be worth trying to use a different server port, altho i dont know if any other than netgear hate port 6667. I'm assuming you cant dcc send on any of the puters on the network?
As for the resume, could you before with this router? NAT/ip probs are usually the culprit there. Use the search feature here, all forums, you may find some tips/urls that will help even if they arent specifically for SMC
