wireless adapter connected, no internet

This is regarding a Dell Inspiron 6400 laptop. the intel pro wireless adapter as well as the broadcom adapter connect OK Even with McAfee disabled (no firewalls) no internet connection is available and I cannot ping any addresses listed by ipconfig. I've tried everything I can think of, running the wireless adapter with WZC and then using the Intel software, minimizing the number of protocols - I now have Client for MS Networks, File and printer sharing, QoS, Network Monitor driver, IPV6, AEgis, WLAN transport, and TCP/IP - nothing makes any difference. DHCP is enabled.
Another problem is that Internet Explorer always exits with an error message.
If I try to repair connection I get Windows cannot disable the wireless adapter. Similarly with ipconfig /release /renew. If I run those I get limited or no connectivity.
Dell diagnostics reports all well with the adapters as does msconfig.
Can any one help? this one's driving me crazy.

Finlay