AD users, network homes, and wireless

OK, bit of a puzzler here and would appreciate any tips. Have a room full of Macs, some iMacs, some MacBooks. The iMacs are wired, MacBooks use wireless. The Macs are bound to an AD and OD, and the iMacs work pretty well; the home folders are correctly used on AD. The MacBooks however will not use the AD home folder over SMB, they will just use a local home folder (although they will add the user's network home to the Dock). After further investigation this appears to be caused by the wireless. If I pull the ethernet out of one of the iMacs, it won't use the home folder either, it will create a local home for users. Plug the ethernet back in and restart and it's all happy again. Is there a hidden behaviour somewhere that forces Macs to use a local home on wireless? Or is this related to network availability during boot. Anyone know a way around this? On a slightly connected note, is it possible to force the ability to sync the user's home folder with an AD and SMB based home folder? Thanks for any advice!