Theres an issue with several series of HP laptops that has been kept quiet for a while now, and thats an issue with the built in wireless card, usually in dv6000, dv9000 and dv2000 laptops.
The wireless card can intermittently not work, due to whatever hardware/software incompatibilites are going on. I myself have a dv2116wm that is sitting in a HP repair shop somewhere due to the problem
If you want any more info:
However, HP hate to admit that it is a reoccuring problem, so if it does happen, you have to push for a repair.
On the other hand, it may just be some models.