Hi Ben,
As JohnWill suggested it looks more like a driver/issue with the DELL wireless N card.....
SCRUBBED AS WRONG CARD....Rest still relevant.
You have download the latest driver but please double check this is the same one I can see on dell below:
http://support.dell.com/support/down...&fileid=259101
Try rebooting the laptop and boot into Safe Mode with Networking (press F8 when Laptop starts).
Uninstall the old drivers.
Control Panel......Add New Hardware.
Install new device/driver.
Reboot into normal mode.
View Available Networks and on the left hand side click Choose order of preferred networks. In the next screen delete all stored wireless profiles.
Then again View Available Networks and connect to you local wireless. You will need to enter the wireless security key again.
See if uninstall/reinstall drivers and deleting stored wireless profiles as just described above makes it more stable?