Hi,
I have a BOXI3.1 SP7 FULL installation, and the dll in E:\Program Files\Business Objects\BusinessObjects Enterprise 12.0\web services\en\dsws_consumer\data\dswsDotNet2Api folder shows it is 12.7, which is XI3.1 SP7 version.
You might want to check out the SP7 installation log for the clue. Sometimes, it maybe the antivirus that interfere the patch installation and upgrade.
Hope this helps,
Jin-Chong