Mac OS X accessing Windows Share
Apple moved to SMB2 in Mavericks.  There have been many reported issues regarding Macs using SMB2 to access Windows shares.  There's even a site dedicated to this specific set of issues!

For a dated, but good explanation of work-arounds see this ZDNet article.

TL;DR

Have your users try cifs:// instead of smb:// (assuming your Windows share supports CIFS)...and hope that 10.9.4 comes with an SMB2 fix. :)