You’re getting a “could not load file or assembly” error message for some Umbraco package that you’ve already installed. You’ve searched for and deleted every reference to said package from code and removed the dlls from bin.
It continues to happen, making you want to stab things.
Touch your global.asax file. No seriously. Apparently that clears the plugincache. Or something. Sigh.
Back Story and Source
Once upon a time, I installed the CMSImport plugin on Umbraco 7.0.1. I needed to import some news articles and it looked like the tool for the job.
It was great! I imported all the things and it worked and birds sang and people were all happy and stuff. But then it was over, I was finished with CMSImport and did not want to import things anymore. So I uninstalled it. Because that’s what you do in these situations.
This seemed to make my installation very unhappy. I guess it missed CMSImport. It started throwing weird errors when I did things like delete a media file. The ghost of CMSImport was haunting me without leaving a trace in the.. trace… log. Anyway. To cut straight to the point, when my weeks of randomly deleting files and sporadic Googleing failed as if no one in the face of the internet has ever had this problem before, I bit the bullet and upgraded to 7.0.4.
I won’t get into how I had to try that 3 times and then ended up not even running the installer. (grrr). Lets just say that when I loaded my fresh installation and deleted a file, I got the same error.
Then I stumbled across this throwaway comment on a completely different issue (emphasis mine).
…could you try touching the global.asax file (just put a space in it and save it) to see if that helps? Sounds like the plugincache is in an invalid state and this helps clear it.
So I did that and it worked. I hope it works for you.