Mac OSX 10.6 leaves open files on Windows Server
Solution 1:
It could be as simple as Spotlight (the MacOS Search mechanism) is indexing those files once the shares are mounted. I believe that there is a preference to turn off the indexing of network shares.
I don't have facilities to test right now, but you could try:
Try running
mdutil -i off /path/to/volume
to turn off indexing for the relevant volume. If that works you could set it up as a script to run at startup or login.You could also try creating an empty file called ".metadata_never_index" and placing that at the root of the network mount point. It should prevent spotlight from indexing the folder and subfolders (at least under that mountpoint.)