Are you using WEP for security reasons? And you get connectivity issues when using WEP?

Then disable it. WEP offers negligible security - attacks against it are trivial (and automated.) MAC address ACL's are also pretty trivial to defeat with a card which allows you to configure MAC address (most do these days.)

Go for something like IPSec or Kerberos (in fact Symbol 802.11 has Kerberos integrated - kewl) or newer kit with TKIP and TLS.