Check modules folder if you have some old files laying around. My guess is that you still have pieces of an old package there somewhere. Or in bin folder...
Compare vs a fresh alloy site with addons installed if you can't locate...
Thanks for your answer. Removing all packages and installing them again did the job on my local version of the site. However on our Azure environment the problem persists. Any other things I could try?
Compare bin folder and modules/modulesbin folder and try to find the difference...somewhere you got some extra dlls you don't want there.
This is my 1000nd forum answer btw. Yey :)
I believe Daniel's solution is what you have to do:
How I fixed it:
1) Installed an older version of LanguageManager (latest 1.x) with NuGet.
2) Manually changed references from LanguageManager 2.x to LanguageManager 1.x in module.config/web.config/project files which NuGet somehow didn't do for me.
3) Restarted IIS.
Our EpiServer CMS 7.5 site uses the LanguageManager add on and recently we're experiencing problems with this. Our users who have this plugin installed can't login anymore. When I try to go the Add-On management screen I see a popup with the following error:
I already installed all latest versions of EPI libraries and the languagemanager via Nuget. Any thougts?