Vlad:

What Opportunistic Locking and SMB settings are you using?

Can't say I recall having run across this exact problem but then we no longer officially support Windows 2003, less than 5% of our clients still haven't upgraded and it has been years since we last had to troubleshoot a problem with Windows 2003 (due to the lack of users not because of the software quality).

To avoid problems like this we recommend that all users access Adagio the same way. In your scenario, option B would be the most appropriate.