Windows Vista - http://www.vistaarticles.com
Windows - Delayed Write Failed or Windows was unable to Save Data
http://www.vistaarticles.com/articles/146/1/Windows---Delayed-Write-Failed-or-Windows-was-unable-to-Save-Data
By 
Published on 11/23/2006
 
Provides a resolution for an issue that occurs when you try to copy a file that is larger than 100 megabytes(MB) to a server location by using the Web Distributed Authoring and Versioning (WebDAV) service.

Windows - Delayed Write Failed or Windows was unable to Save Data

This problem occurs because, during a WebDAV connection, the WinInet function does not break up the data into sufficiently small chunks. As a result, the system cannot allocate a sufficiently large block of kernel pool memory, and therefore the file-copy operation is unsuccessful.

Details: http://support.microsoft.com/kb/818408/en-us?spid=2073&sid=global