Laptop wireless suddenly cut out

My wife's laptop, a Dell Inspiron 1501, had been working fine for a couple months (it's new) but today its wireless connection suddenly wouldn't connect. I'm not exactly sure what info is needed for this issue, so bear with me. Here's what I'm working with:

Laptop: Dell Inspiron 1501
Wireless card: Dell 1390 WLAN mini-card
Router: Netgear WPN824v2

I'd set up the wireless connection successfully a couple months back (using WPA-PSK [TKIP]) and her laptop has had no problems using the wireless since then. Then today she told me it just wouldn't connect. I got around the problem by disabling Dell's WLAN wireless tray manager and letting Windows manage the connection, but now her listed speed has dropped quite a bit. Before it was always listed at 56 mbps; now it's usually at 18 with spikes up to 24 to 32 mbps. Is there something I can do about that?

m19