If after running upgrade.bat as suggested by Chetan, it is still not working, you can try to repair your installation. It seems something has gotten corrupted.
Do you have a replication server in place?
If not, I would suggest you be pro-active and implement Disaster recovery immediately.
http://www.symantec.com/business/support/index?page=content&id=TECH102333
What you are indicating could be bad sectors on the disk or a failing disk itself.
Are you seeing ATAPI errors in the event logs when you were trying to delete packages, possibly a loss of communication with the dive?
After preparing disaster recovery, try and run some diagnostics on the drive(s) to see if any are having issues/troubles.