Surprised to read your post ldm. I was previously with Kaspersky and the daily updates from them seemed to take forever! Everyone blamed their servers. My installation with eset was lightning fast, and so has been the daily updates so far.
If you google 'slow internet security updates' you'll find most of the leading security suites being complained about by their users. Notably KIS and Norton, being the worst offenders.
Assumed you uninstalled your old security completely? I've always used CCleaner :- hxxp://www.filehippo.com/download_ccleaner/
to clean the registry after uninstalling any program. (It's free! and safe) - Gets rid of the remnants that might cause conflict with a replacement.
Apart from that, can't suggest anything else.