Wireless network suddenly stopped working

So there are two laptops in our house. Mine is physically connected to a
modem and has a wireless card to send a signal to my flatmates computer.
This system has worked fine for about a year and half, until last week, when
my wireless card stopped sending any signal. It doesn't light up, and when
my flatmate's functioning wireless card is inserted into my computer, it also
doesn't work. It works in his computer, though.

Then we brought my laptop to an IT expert, who we thought fixed the
situation. He made it possible to for my computer to connect to the
university (we are students) network, and the card started lighting up again.
As soon as we brought it home and it no longer gave off a signal. It
stopped working 10 days ago, and we don't understand why. We never actually
installed software when we started using the card, so we're not sure it's a
problem with the driver.

Any ideas, or suggestions regarding this problem are greatly appreciated.

Thanks.

~Sue