Sitecore Package Designer error: System.Reflection.ReflectionTypeLoadException: Unable to load one or more of the requested types

When trying to use Package Designer, sometimes you will get a cryptic message like the one below:

System.Reflection.ReflectionTypeLoadException: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.

If this happens, don't fret, simply follow these steps:

1) backup the bin folder of your application.
2) Install the same version of sitecore on another machine, or in another directory.
3) Copy all the dlls from the bin folder (except for the instance dll eg sitecorewebsite.dll)
4) Paste them in your folder.
5) Voila this should solve your problem.

A co-worker of mine found this solution for me.  Here is the original link:

Sitecore error in package designer installation wizard/

Hope this saves you some time on this issue.

If you are just starting out with Packages be sure to check out this article by Alex Shyba on
Things To Consider When Using Sitecore Packages