Problem with wep encryption

Hi,

I have got a 3com OfficeConnect (3CRSHPW196) pcmcia card with atmel 
chipset and I use the kernel included drivers by Simon Kelley (kernel 
2.6.5) on a gentoo system.
As long as I do not use wep encryption everything works as it should but 
  with enabled encryption I do not get any connection to my accesspoint 
(it is a d-link dwl2000+).
iwconfig displays the right key and even shows the mac adress of my ap 
but I get no signal level or link quality and there won't be any 
traffic. Iwconfig does further not show any packet statistics like 
invalid crypt or anything else just ifconfig gives the number of faild 
packages.
The pcmcia card is ok (at least it works on windows clients with 
encryption).

May it be any problem with the driver or has anybody got an idea what it 
could be? I have allready searched the web a bit but I did not get any 
helpfull information until now.

I would be pleased for your help, Sebastian