Studio 1735 & 5GHz wireless networks

I have a brand new Studio 1735 notebook.  Although the reception on 802.11n 2.4GHz networks seems to work fine, it doesn't get hardly any reception on 5GHz networks.  The notebook has a Dell Wireless-N card in it, whereas the last Dell notebook I bought had an Intel card in it, and that old notebook works fine with 5GHz networks.  Note that I have tried both Linksys and D-Link routers with my new notebook.

Has anyone else had problems connecting to 5GHz 802.11n networks with Dell Wireless-N cards?  Or could it be something in the notebook, like a bad antenna connection to the card?  Since 2.4GHz networks work fine, I wouldn't think that would be the problem.

Will Dell fix this problem, or do I have to buy a new wireless card myself?

Thanks in advance,

Shane