On a Windows 7 or Windows 2008 Server R2 machine, you may notice a significant delay saving your Excel 2010 documents into a My Documents (or subfolder like My Pictures) that has been re-mapped to a network location by a group policy. The behavior does not occur every time you save the document.
This problem is caused by a network driver on Windows 7 and Windows 2008 R2 machines
To resolve this issue, download the hotfix to update the network driver from KB Article 981711 (http://support.microsoft.com/kb/981711). This hotfix was created to address a different problem that you may not be experiencing.