While exporting updates from WSUS server zero-size output files is generating and sometimes the result is “Fatal error” as shown below.

Error:
Export failed to export updates. Please look at the log file for error details.
Fatal Error: Error in the application.

This issue is due to a file size limitation in the CAB file format.Microsoft has released fix for this issue, Please download and install this patch.

Download Fix For Windows Server 2012 – http://support.microsoft.com/kb/2819484 

Download Fix For WSUS 3.0 SP2 (WSUS 3.2)  Windows Server 2003 R2

Download Fix For Windows Server 2008 , Windows 2008 R2 Server