If you un/re install, make sure LU gets uninstalled, then purge anything Symantec from the drive and registry IF you have no other Symantec products. Keep in mind that they share a lot between products - pcAnywhere and so on so don't get too radical unless you are sure.
I've seen SEP uninstall but LU remain or parts of it.
In the cases here, SMS has actually been causing fits with upgrades and reinstalls! It's attempting to push updates and locks up the MSI installer services wreaking havoc - so look beyond the Symantec product as possible causes, too.