If you opened a file using a UNC path and subsequently try to save it to that UNC path, you may receive an error similar to one of the following:
Cannot read file. File is locked
Your event log may contain:
Event Source: Application Popup
Event Category: None
Event ID: 26
Description: Application popup: Windows - Delayed Write Failed : Windows was unable to save all the data for the file <FileName>. The data has been lost. This error may be caused by a failure of your computer hardware or network connection. Please try to save this file elsewhere. For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
This is likely to be a bug.
Until it is fixed in a Service Pack, you can try a workaround by setting the EnableOplocks data value to 0.
NOTE: You must restart your workstation for this setting to become effective.