User-734925760 posted
Hi,
According to your description, you made some changes for the Visual Studio then the web.config file can't be edited.
So far as I know, it 's because the dll file is replace as you update the Visual Studio, this DLL file is installed by the VS 2010 installation. So I suggest you to re_install the Visual Studio.
There si a similar thread, please refer to the link below:
http://social.msdn.microsoft.com/Forums/en-US/d65c71f5-3887-4f2a-bbd3-e799a4ac6fdc/visual-studio-database-tools-error
If you do not want to re-install the vs, please refer to update the config in IIS, please refer to the steps from the link below:
http://help.globalscape.com/help/eft6/mergedProjects/SAT/Editing_the_Configuration_File.htm
Hope it's useful for you.
Best Regards,
Michelle Ge