If you are using Samba 3 and have issues with Windows 7 clients connecting to the share, the easiest fix is to upgrade to Samba 4.
A recent Windows security update released in Fall 2014 causes an error in Samba “Server exit (failed to receive smb request)” and on the Windows end “The specified server cannot perform the requested operation”. This appears to be compatibility issue with Samba 3.X and Windows 7. Rolling back the Windows update makes the problem disappear. So, the best option is to upgrade to Samba 4.
Before you upgrade, make sure you back up the existing smb.conf file. Upgrading Samba will overwrite the existing smb.conf file. In RedHat, use yum to remove the samba-common and samba libraries and install the samba4 package.