I get similar issues when ever I've tried to do it from within the Security Center except that in my case it says "network error", which is absurd as I'm not on one.
Anyway, as they are Artemis they already have been checked and not found in the database so it may be a good idea to send them up, especially if they are false positives.
Check this sticky regarding the procedure:
http://community.mcafee.com/showthread.php?t=227790(You'll see there that they are now accepting larger submissions....unofficially).