This is quite strange. I searched TAC open/closed cases and the bugs and did not find anything similar.
I know the guys I work at Cisco have 4.0.2.627 CSA and Cisco VPN client along with Cisco Aironet cards, both pcmcia and mini-pci cards. They use their PCs at coffee shops and hotels and VPN with no problem.
I am not sure if the Cisco deployment has the network shim enabled, though.
In order for the Developers to help you, you may want to include the info about which wireless card and software you are using.
You may also want to let us know which CSA version you are using - easy to tell by a right-click on the flag and click on about (you probably know off-hand).
Also, have you looked at the local CSA log file on the PCs having problems? I doubt you will find anything extra there, but it is worth looking at. Look for CSALOG.TXT under the CSA install directory.
Sorry I could not be of more help.
peter