Hi,
The error is mostly caused by the version you have installed on your computer does not match the version of the EO.Web.dll that your project references. The installer never changes the version of the DLL that your project reference. So please check that first.
If the first step reveals that it is a version mismatch, you can either reinstall the version that your project is using or modify your project to reference the currently installed version. To change the version your project currently reference, go to solution view and delete EO.Web.dll either from your "bin" or "reference" folder and then re add it. Make sure you delete any .refresh files in your project's bin folder before doing so.
If the version does not appear to be the problem, it may have to do with security settings. Make sure the project is a local project (not on a network drive), or following instructions outlined here:
http://www.essentialobjects.com/ViewDoc.aspx?t=InstallationAndDeployment%2ffor_vs2005.htmlThanks