Interior cold air

I have a 01 Tahoe, evey since I got the wife has complained how cold she is riding with me. I blew her off as being a freezy cat. Well 2 weeks ago I was going snowmobiling with a buddy. It was about 28 below while driving up, he took over driving for a while. Well needless to say I had to call the wife to apoligize. There is a ton of cold air coming from under the dash. There is a metal box under the dash that actually had ice on it! My question is, do you think this is normal or could there be something wrong. If this is just how the Tahoes are does anyone have a fix for it? I was going to try to stuff some insulation up there, but firgured I would post here first. Thanks.

Here ya go.

http://www.automotiveforums.com/vbulletin/showthread.php?t=481128

Thanks Jeepin, I figured there was something to it. I am going to talk to my dealer about it.