Interesting Wireless Networking problem

[Q8Wireless]

I have a strange problem with a wireless network I setup for a customer. I hope somebody will give a clue.
It started with a single AP D-link DWL-900AP+ with two PCs that are connected with D-link DWL-120 USB and a laptop with D-link DWL-650+. It was working perfectly as long as the laptop stayed in the area of coverage of the access point. then the customer wanted to use the laptop in another area. So we made a UTP cable connection to that location and setup another access point D-link DWL-1000AP+. Then problems started.
The laptop works fine in the DWL-900AP+ area but when moved to the DWL-1000AP+ it sometimes works and most of the times it does not. When I ping the DWL-1000AP+ from the laptop it gets a reply but it cannot get and reply from the DWL-900AP+. However, when I move the laptop near DWL-900AP+ it is working and can ping all PCs. At all times I can ping DWL-1000AP+ from PC1 ot PC2 connected to DWL-900AP+. so from this we know
1- No problem with cable: because I can ping the DWL-1000AP+
from PC1 or PC2.
2- No problem with the DWL-900AP+: becuase All PCs connected it working fine.
3- No Problem with the DWL-1000AP+: becuase laptop can ping the AP when it is directly connected or connected to the other AP.
4- No problem with the laptop: because it is working when it is near DWL-900AP+

Can anybody suggest anything?
Please check the drawing attachment which shows the setup.

[Q8Wireless]

Sorry the attachment was not it the first post here it is.

[FireFerum]

Have you tried to set up the Laptop with a static IP which is above the ones the router gives off for DHCP? Also, have you looked to see if there are any MAC address restrictions???