This fixes NetworkManager for me, taken from the ipw2200 driver...

--- ipw3945.c.orig      2006-04-12 20:09:32.000000000 -0400
+++ ipw3945.c   2006-04-12 19:56:36.000000000 -0400
@@ -11639,6 +11639,11 @@
        range->event_capa[1] = IW_EVENT_CAPA_K_1;
 #endif                         /* WIRELESS_EXT > 16 */

+#if WIRELESS_EXT >= 18
+       range->enc_capa = IW_ENC_CAPA_WPA | IW_ENC_CAPA_WPA2 |
+               IW_ENC_CAPA_CIPHER_TKIP | IW_ENC_CAPA_CIPHER_CCMP;
+#endif
+
        mutex_unlock(&priv->mutex);
        IPW_DEBUG_WX("GET Range\n");
        return 0;