Try Nod 32
www.nod32.com
I like this software because we can centrally distribute the software with no major load impact on the client computers. Our remote users are updated once they connect to the internet. Cost pr client is very competitive.
This is a European company who has won numerous awards and is starting to make in roads here in the USA. In our testing, we recieved updated virus definitions hours before Symantec and Mcafee and we have not had any issues of the client computer locking up after a update unlike it's competitors.