Office 2010 / SharePoint 2010 when uploading multiple documents, large files will sometimes randomly fail. (114012011114004)
This is a design limitation of the feature and limitations with 32 bit processes. As memory get allocated by the .NET runtime if a large enough block is not found an out of memory exception is generated and the file upload fails. The level of memory fragmentation at any given time is random.
Use single file upload or upgrade to both Office 2013 and SharePoint 2013 and use the new "Drag and Drop Upload".