Yesterday when restarting Alfresco I got this exception out of nowhere. Never seen it before. It says that some certificate is not valid any more (not after Aug 16 2012). I have no idea what certificate because I didn't add any as far as I know.
The error you are receiving is due to the reason that the SSL certificates for SOLR and the Repository got expired on 16th August2012, which should have been informed to you if you are an Enterprise customer. Please log in to your support portal to get the .bat/.sh file to generate new certificates.