A/C Drier Fitting Won't Tighten

[cyberwolf]

I have been working on replacing the drier on my '98 s90. After getting some larger wrenches, I finally managed to break the nut loos on the old one. Everything was going smoothly until I tried to tighten up the nut on the larger AC line to the drier. The nut fitting threads on easily for a couple of turns and then immediately gets extremely tight and will not secure the line no matter how hard I try. The line seems to fit into the new drier the same as the old one and I just can't figure out why I can't get it completely tight. Any ideas?