This can be caused by the floppy drive check that occurs on shutdown, especially if there is no floppy drive in the computer. To solve the problem, disable the shutdown floppy check.
Recommended to take a back up of the registry before any troubleshooting.
To disable the floppy drive scan
Start the Registry Editor.
Navigate to the following registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\INTEL\LANDesk\VirusProtect6\CurrentVersion\Storages\Filesystem\RealTimeScan
Create a new DWORD value, and name it SkipShutDownFloppyCheck.
Right-click SkipShutDownFloppyCheck, and then click Modify.
Change the Value Data to 1 with the Base set to Hexadecimal.
Close the Registry Editor.
To disable the floppy drive scan through the client user interface
Start Symantec AntiVirus.
Click Configure > File System Auto-Protect..
Click Advanced.
Under Additional Advanced Options, click Floppies.
Uncheck Do not check floppies upon system shutdown.
Click OK and then click OK again.
To disable the floppy drive scan through the Symantec System Center
In Symantec System Center, unlock the server group.
Do one of the following:
Right-click a server group or client group, and then click All Tasks > Symantec AntiVirus > Client Auto-Protect Options.
Right-click a server, and then click All Tasks > Symantec AntiVirus > Server Auto-Protect Options.
On the File System Tab, click Advanced.
Under Additional Advanced Options, click Floppies.
Uncheck Do not check floppies upon system shutdown.
Click the lock icon so that it appears as locked, if applicable.
Click OK and then click OK again.
Alternatively what you can try is to update the symevent driver.
http://service1.symantec.com/support/ent-security.nsf/854fa02b4f5013678825731a007d06af/45c5f0d588d1298a88256a22002726d9?OpenDocument
Please keep us updated in case it doesnt work out.