I am getting this same error in my VS2013 application when I run it on the user's computer. It works correctly on my development computer, however. I did notice that the version of log4net that is installed is version 1.2.13.0. I have the Crystal Reports version 13.0.14.1720. The project properties Application tab has the target framework as 4.5.1.
I used to have to install Crystal Reports on the user's computer but now that does not even seem to be allowed. Any idea what could be the problem?