You have a SEP client that's logs indicate that a scan is still in progress. When you check the client locally it does not appear that a scan is occuring. If you attempt to run a scan on that particular client machine, the scan runs as expected.

If the above is correct, the following should resolve the issue with the log showing a scan is still in progress.

The erroneous information in the scan log is cosmetic and can be safely ignored.
To remove the entry from the scan log delete the log from the day that the scan occurred.
The log files for the SEP client can be found here:

For Windows NT based systems:
C:\Documents and Settings\All Users\Application Data\Symantec\Symantec Endpoint Protection\Logs

For Windows Vista or Server 2008 systems:
C:\ProgramData\Symantec\Symantec Endpoint protection\Logs

Log files may also be found in the user profile.  For example on a Windows Vista machine:
C:\Users\<User Name>\AppData\Local\Symantec\Symantec Antivirus Corporate Edition\7.5\logs

The log files will be listed in a format that incorporates the date of the log in the name of the log file.
For example:
07222009.log is the log file from 07/22/2009, or July 22, 2009.

Regards.