It sounds like its running into problems during the DHCP address request, so the wireless connection itself (the equivalent of plugging in the network cable) appears to be working. Make sure the firewall on the computer isn't blocking the wireless connection. Also, if you are using MAC address filtering on the router, make sure the wireless card is allowed to connect. You can find the MAC address of the wireless card in either the Dell Wireless Utility, or from the Network Properties window for the card.
Dell Wireless 1395 Wlan Mini-card Driver Update
Dell Wireless 1395 WLAN Mini-Card - Driver Download. Dell provided driver for selected Inspiron and Studio models. Windows 7 32-Bit Driver.