Are there any ups or down when using 2 connections from a single machine to connect to the same internet connection? (in this case cable)

I got frisky cuz' my Xfire for some reason won't connect. I had a case where games and stuff would run with one of the cards and not with the other so I was just testing it. Are there any +s or -s of just leaving them both connected?

P.S Didn't solve my Xfire issue. I dunno what's up. It's not the router, since my laptop connects to Xfire fine. I do have a firewall but I've disabled both right now (Sygate and XPSP2 Firewall)

Well the main disadvantage of having 2 network connections is that applications will choose 1, and also your router/switch/whatever might block having 2 connetions from the same IP

There is no advantage whatsoever unless your expecting one of your cables to break?!? If it was me I would just take one out, leave one in.

In the case of using a broadband connection there would be no benefit to this. The bandwidth on your cable connection is lower than what the switch can provide (10/100) so you would not gain any speed increase even if you used teaming software to team the NIC's together creating a single Virtual NIC. The Router/Switch can only provide the bandwidth available from the ISP.

If you could team them and one of the cards died you wouldn't notice it. This is done mostly with servers and would provide very little if any benifit to end users. In all honesty it would probably just introduce more complexity than it's worth.