Desktop File and Print Sharing is limited to 10 Professional and 5 Home Connections.  You can try a Registry setting to increase this.

 When sharing a file/printer, then there is a limit for how many users that can access the shared resource from the Local Area Network (LAN) simultaneously. The actual inbound SMB connection limit (Prof=10)/(Home=5) can be seen by running this command.

net config server

Regedit

Update the following DWORD registry settings

[HKEY_LOCAL_MACHINE \\SYSTEM \\CurrentControlSet \\Services \\Lanmanserver \\Parameters]
MaxMpxCt = 50 (Default = 10 commands)
MaxWorkItems = 256 (Default = 64)
Size = 2 (Default = 1)

Note You can set the number of concurrent SMB commands to a value that is between 10 and 255. The default value is 10. In Microsoft Windows Server 2003, you can set the number of concurrent SMB commands to a maximum value of 65,535.