I just tried a package installation using the MiKTeX 2.8 package manager
(administrators version) and got the following error:
Windows API error 87: The parameter is incorrect
The solution was posted here:
As Marius posted,
"I had an instance of MikTex open which was blocking the files needed for the install. After I closed the MikTex instance the install worked fine."
Is the error msg above as informative as possible?