fusion 3.0 not connecting on 802.11b AP's

Are there settings that needs to be done on new MC's with fusion 3.0 or the Jedi chipset to connect to an 802.11b AP without any encryption?   

One of our customers are still using AP4131 (no encryption) with MC9090's without any problem but their new MC3190 CE6.0  gets disconnected after a few seconds . 

Another customer were also  using a very old LXE AP (an AP with 2 802.11b pcmcia wireless cards) with MC9090-G (no encryption)  but their new MC3190-G  and  MC55will connect for a while then will get disconnected again.    They do not want to used encryption since their old LXE mobile computers is not capable of encryption.

Any help is appreciated.