I've experienced a lot of anomalous behavior from our Macs on our windows servers. They seem to do weird things with file locks.
For instance, if they have files in a folder and want to move them to a folder inside that folder, they get denied the request. They get told they don't have the permission. If they copy the files, paste them to the destination, then delete the original, everything works fine. Theoretically this is all the move command does, but this behavior would prove otherwise.
I know Macs emulate windows clients better than windows servers emulate macintosh servers. They're still far from perfect, using the same user #s on the network instead of a GUID. (Not that Windows servers don't have their own problems.)
We're on OS 10.3.9 right now, preparing for a 10.5 migration. I hope the samba implementation has improved some in the meantime.