Hi there
This can often be an issue with security encryption. There may be a wrong key entered or the client adaptor does not support the encryption used.
To try and solve this first change the SSID on your AP so your laptop will be forced to create a new profile. Then set security to basic WEP 64bit and try to connect again. Update the wireless adaptors drivers.
If you have any third party Firewalls, try and temporarily disable them to make sure they aren't blocking it.
Good luck
Dale