-snip-
I can say for sure that EVERY SINGLE case I ever read about how "Electrum stole me" or "Electrum is unsafe" turned out to be the user's fault. EVERY SINGLE ONE OF THEM. I (plus a HUGE part of the community) am using Electrum for over 2 years and I trust them. Even after this security issue, I have never seen a single case where someone lost their funds due to this exploit. So, IMHO that was (probably) your fault.

1. Norton AV can't find every viruses. And if you had a malware, a big password doesn't mean anything.
2. Are you sure that you downloaded the wallet from Electrum.org? I can remember at least 2 cases where the user claimed that he did while he actually downloaded a fake software from electrumwallet.com or something similar.