Loosing wifi connection irregularly

Hi,

I have an Macbook, bought this year, and have an annoying problem. When I use this Macbook wireless on the university campus, I have no problem. When I use it wireless at home, having a connection or not varies for an unknown reason. The wifi-accesspoint is not the problem, because another laptop can connect to the accesspoint without problem. On the Macbook, it varies: connecting easily, connecting after some time (using wired at first), connecting and loosing, not finding an accesspoint at all, connection to the accesspoint but taking forever to connect to websites or the server.

I ran the systemtest (restart + D) and found no problem.

Can somebody please tell me what may be going wrong?

Thank you.