I had the same problem as you have: everything worked fine when I plugged the WebGear card into a cheap AMD computer that had all the devices (video, audio, ethernet) on board, but failed to work when I moved the card into a more expensive computer with all these devices as external PCI cards.
I scratched my head for about 1 week, installing various kernels, playing with various PCMCIA versions, until I realized that something must be wrong with the interrupts. I took a look at the laptop I'm using as the other wireless computer to see what interrupt the WebGear card uses and observed a difference. The laptop is using irq 3 while the new computer was using irq 9. So I went ahead and I disabled the onboard serial port 2 in BIOS which was using irq 3. Voila, the whole thing started to work again!
BTW, it may help to try disable all the unused controllers that eat up irqs, as it appears that disabling only COM2 somehow doesn't solve the problem.
I hope this helps.
Good luck, Ovidiu