Saving datafiles that are posted on a SharePoint site results in all updates lost.
When opening a datafile from the SharePoint site SPSS will save it to a temporary location on your harddisk.
It is possible to work with the datafile, but when you try to save the changes the temporary file is updated but not the original file on the SharePoint site.
Currently saving to an URL (Sharepoint) is not supported.
Resolving the problem
An enhancement request has been created.