Please check this KB aticle for a possible solution
"Could not scan [#] files inside [path][filename] due to extraction errors encountered by the Decomposer Engines" during a scan
http://www.symantec.com/business/support/index?page=content&id=TECH99755&actp=search&viewlocale=en_US&searchid=1308852718042
! am moving this thread to the Endpoint Protection forum for greater visibility.
Best,
Thomas