Wireless setting after Ghosting Image

First post here so hopefully I'm in the right place.
Our (school division) scenario is this:
We have 60 Dell D510 laptops at a school. We use Ghost Solution Suite 2.1 to
create and push custom images via a wired network to these units.
We have 7 Dlink DWL71000APs running throughout 1 wing of this school for the laptops to connect to. We are using 128 WEP keys (I know we should use WPA and will be moving back to them after this issue is resolved) and each AP is setup exactly the same (network name and SSID) except 2 are set to channel 1, 3 to channel 6, 2 to channel 11.
When we tested after the images were pushed we saw each one connect in turn
to each AP. As we turned each AP off each laptop would "jump" to another AP.
The laptops are set to connect at logon.
Problem is that out of 60 machines, only 20 are still conecting. The others see the SSID but will not go any further.
If we logon onto a machine with local admin credentials, we can see all 7 APs but cannot connect to them.
I only have some basic wireless skills, so any help would be appreciated.
Thanks in advance.

Anyone?
Is this the right group?
Do you need some more info?