Claudia,
What OS do you have? Are there any other devices attached to the laptop, such as USB or PCMCIA cards? Where did you install the wireless driver from?
This is probably a long shot, as it could be there is actually something physically wrong with the card, but here are a couple things you might also try:
1. If 2000/XP try booting up in safe mode with networking enabled to rule out another device possibly interfering in terms of a resource conflict.
2. If XP, you might want to try restoring the system to an earlier restore point when the card was working (as a precaution, create a restore point before you do this).