Hi,
Please try to set it as early as possible. Setting EO.WebBrowser.Runtime.CachePathin fact is a short cut to EngineOptions.Default.CachePath. So it will have no effect if it is set after the default engine has been created (when the first WebView is created), or you explicitly set any engine options (at which point the default value was copied).
If you still have problems, please try to isolate the problem into a test project and send the test project to us:
http://www.essentialobjects.com/forum/test_project.aspxOnce we have that we will be happy to investigate further.
Thanks!