It has been a long time since I had a rundll32 error. Probably dates back to two or more years. My solution was to find file in Windows>system 32 folder, change the file name. Then I conducted a search for rundll32.exe, downloaded and copied it into Windows>system32 folder.

I know that it is risky to download a system file from the net. I would only use this solution when everything else has failed.