Well, okay, the ipw2200 works fine if I turn off all security on the AP,
but the 2.6.15-rc1 version can no longer connect to my WPA/WPA2 network.

The same driver version out-of-tree works fine on 2.6.13,
but not on 2.6.14, nor in-tree with 2.6.15-rc1.

The syslog shows:

 >ipw2200: Intel(R) PRO/Wireless 2200/2915 Network Driver, git-1.0.8
 >ipw2200: Copyright(c) 2003-2005 Intel Corporation
 >...
 >eth1: NETDEV_TX_BUSY returned; driver should report queue full via ieee_device->is_queue_full.
 >...
 >ipw2200: U ipw_best_network Network 'RTR (00:13:46:16:96:b8)' excluded because of privacy mismatch: off != on.

That last message shows why it couldn't connect ("RTR" is my WPA-enabled AP),
but that's more of a symptom than the underlying problem.

Full debug trace attached

Cheers