You will need to decrypt disk before making any changes to OS
http://www.symantec.com/business/support/index?page=answerlink&url=http%3A%2F%2Fwww.symantec.com%2Fbusiness%2Fsupport%2Findex%3Fpage%3Dcontent%26id%3DTECH176187%26actp%3Dsearch%26viewlocale%3Den_US&answerid=16777220&searchid=1326480208844
Install 10.2 MP3 which includes lots of fixes for MAC.
Download from fileconnect.symantec.com