I'd just installed my certs correctly into my Plesk 8.3.0, I encountered some trouble with the "CA didn't sign the certificate" warning message but I solved it.
Right now it seems to me that I installed certs in the right way for my domain, but... Chrome, Firefox, they still saying that the cert is expired and auto-signed... I really don't know how to fix it.
On Firefox I got this message:
Il certificato non è attendibile in quanto autofirmato. (autosigned)
Il certificato è valido solo per plesk. (plesk valid only)
Il certificato è scaduto il 04/03/2009 13:01. La data corrente è 22/04/2011 10:00. (no more valid)
(Codice di errore: sec_error_expired_issuer_certificate) (error code)
I checked the server date/time and it's everything OK, anyway, this seems to me that Plesk didn't "catch" the new cert...