The first thing to do is to check the settings used.
Check the encryptions settings. Are they the same on both PC and laptop?
Same protocols?
Check the router's settings. Any exception for the laptop?
Try placing the laptop somewhere else (another room, another location in the room, closer to the router) or orienting it diferently.
You may have to much interferences and the laptop don't/can't transmit with enough power.
If possible, try to connect the laptop to the router with an ethernet cable. It things wotk correctly that way, you may have some problem with the wi-fi transmition, maybe only for the upload part, like a broadcast power level that is to low.
Maybe a neibour have some new whireless device that may be causint poor performance on your side.
Try switching to another channel or increase the emition power of the laptop.
Electro, January 2012