I have a XPS M1330 which I recently upgraded to Windows 7 64-bit. Following the upgrade, I found I wasn't able to reliably (mostly not ever) access or even see Wireless N routers which were using the 5GHz band. I confirmed this with two different routers (Apple Airport Express and Linksys WRT610n).
Ultimately, what I found corrected the problem was to uninstall the driver for the Dell 1505 wireless card (and check the box to delete the driver files) via Device Manager. When Windows "re-discovered" the card and installed drivers from its driver store, I was able to associate with the 802.11n router fine.
I made the mistake of allowing Windows Update to install an "updated" driver and my problem came back so I had to go back and redo all those steps again. It appears that the driver titled "Broadcom driver update for Dell 1505 Draft N WLAN Mini-Card" has issues.
I tried to get help for this issue with XPS Technical Support and was told that this was an "advanced software configuration" issue and I would have to be handed off to a fee-for-service tech support group to deal with it. I can't say, particularly given how I was able to fix the problem, that I consider this an issue that XPS tech support should not have handled (or been able to handle). This is the first time I've had a bad experience with XPS tech support on an issue.
Thanks that solves my problem when I did the free upgrade to Windows 7. I was unable to connect or upgrade my windows 7 and XPS customer service refused to refund and return the 1505 Lan wireless I had spent $70 to upgrade in October.
I had the same terrible bad experience with the XPS tech that I have decide not to buy Dell (having purchased six previous with not one problem). I believe Dell is totally unaware of problematic outsourcing of customer service which has policy of refuse to refund at all cost and to sell added services(for $90.00 you can upgrade to a technical service rep from United States) and various computer products to an already unhappy customer.
Thank you for the simple, easily-overlooked solution. I too recently upgraded my Dell notebook/laptop (Latitude D630) from Windows XP 32-bit to Windows 7 64-bit. Initially the (Broadcom) Dell Wireless 1505 Draft 802.11n WLAN Mini-Card was able to connect to my Linksys/Cisco WRT610N router using 802.11n (5 GHz) with no problem, but after letting Windows 7 "update" the driver for the wireless card, I could only utilize 2.4 GHz. So, thanks for sharing your solution, as it works! Now onto making sure that "automatic updates" with Windows 7 doesn't cause the problem to reoccur.