If the Dell has two slots and the card will fit either, try the other.
Also check Dell site for updated drivers.
Have you tried any other PCMCIA device in the slots ? Can you try the Air Card in another computer ?
Yes I tried the card in my Toshiba with XP and it works fine. My IT people are telling me that they have the same issues with several other cards used by other Field Tech's like myself.
The Dell only has one PCMCIA slot, the IT dept. is having a hard time finding a driver to support the 875 Air Card.