Endpoint Protection

I use Symantec Endpoint Protection as unmanaged client.
I configured to update virus definition files every four hours, but sometimes can't update it.
Once failed to update, I can't update until "Remove All Files From Cache" in Control Panel.
After finishing it, I can start updating again, but it's a bother.
And sometimes in the worst case, I have to uninstall / reinstall SEP.

Can somebody help me how to solve this problem?

Try to use pull method for update. Make LU run continously

I presume if you manually run LiveUpdate at the endpoint, nothing is updated then either. Correct? 

If so, this sounds pretty strange. I would suggest you contact support on this one.

Could it be a corrupt LU component possibly. Maybe a reinstall after wiping your present install will work

If I run LiveUpdate manually, the message shows that there is no new definition file, but my colleague PC can update to newer version.
So, if I don't remove files, it can't be updated more than one week.

I tried to reinstall after delete all related files of Symantec, but a few days later same problem happenes.

I'll contact Symantec support.

I visited support page of Symantec and tried to find how I can contact support, but failed.
Can you let me know how to contact support?

http://www.symantec.com/support/index.jsp

Make sure you check the correct country it the top-right of the page to get the right numbers.