Could not load file or assembly 'Microsoft.Crm.Tools.Admin.DMSnapinLib' or one of its dependencies. The parameter is incorrect. (Exception from HRESULT: 0x80070057 (E_INVALIDARG))
We fixed this error by clearing out the Asp.Net temporary folder under the Microsoft.Net\Framework64\v2.xxxxx folder. After that we had to restart IIS before we were able to load up the site.