After I change my MAC address I can no longer use TCP (but UDP and ICMP works), because the AP wrongly resolves my MAC address as the broadcast address (FF:FF...:FF) instead of the new MAC I assigned.
If I change it back to the original MAC everything works.
I wonder if, even though I changed the MAC (macchanger -a), ndiswrapper still uses the original one in another packet and because of the confusion I end up being resolved the FF:FF...:FF at the AP ...
It a wireless Intel 2100 with, obviously :), ndiswrapper. Kernel 2.4.27.
Thanks in advance, Eduardo.