This is on a server we had updated to SP2 a couple of days before. The main symptom is being unable to login to the the control panel. You get a popup message saying: "Unable to exec utility packagemng: Unable to create pipe." and then some pipe and file names.

The real problem seems to be PLESKMISCSRV. It gives the error "Error 21: the device isn't ready" when I try to start it. In the application log, I see it failing to start with the following:

can't find authentication package (Plesk{87824292-B2FB-4722-AF4A-55170C150F72}): (1364) A specified authentication package is unknown.

Anyone have any ideas?