I have seen multiple threads regarding this on the steam forums. There the going gossip is that it is a known norton issue and their customer service department assures its users they are working on it. That being said...
IMHO Norton AntiVirus is a virus in itself. You are installing a program
guaranteed to suck up a large chunk of system resources which will protect you from 83% of known viruses which
may suck up some system resources. I had it and paid good money for it. After a series of failed laptops(another story) and continuous reinstalls, my copy was flagged for having been installed on too many machines. After many aggravating phone calls explaining I had only installed it one one laptop at any given time and that they were my personal laptop each time, I am told to send it in to the company, wait 6-8 weeks and they may be able to re-enable it.
Do yourself a favor, and uninstall norton now. Consider any money paid a sunk cost...lost to the lesson that just because they pay for the most shelf space at your retail box store doesn't mean they are the best product. I use NOD32 and love it. Low system resource use, blocks most issues, never bothers me, updates on its own, cost very little $$$$(trial version is free & full featured).
