I have a DLink router in my possession that does not work with Orinoco cards when WEP is enabled. It doesn't flat-out not work. It simply behaves strangely (a lot like you're describing). I had an email dicussion about it with a senior level Dlink tech and he bacically told me that I should buy non-Orinoco cards.

Though this might not solve Justin's problem, it does solve one I had.
See, last month I bought a new laptop, with an internal 802.11b card. It's also an Orinocco card. And I can't for the life of me get it to work with my US Robotics wireless router when WEP is enabled. The thing connects, but it looses it's connection about half a minute later.
So, the problem is with the Orinocco card? Hmmm, I had my suspicions, since it doesn't comply to the WiFi standard. Guess those suspicions are now confirmed.
Thanks Rob !