Cannot enable feature with feature receiver via PowerShell
I have the same issue. The curious thing is when you open up a new SP2010 powershell window and reissue the same command the assembly is found without any problems. See:http://khurramdotnet.blogspot.com/2011/01/enable-spfeature-command-throwing.html
Try this: go to the Control Panel, click on "Programs", click on "Programs and Features", select "Microsoft SharePoint Server 2010" (or whatever you have installed), click "Change", select "Repair" and click "Continue". This is what helped me.
Try this: http://geoffwebbercross.blogspot.ca/2011/06/failed-to-create-receiver-object-from.htmlIt worked for me, I did not have to change a stitch in my code / solution