Hmm...regarding the proxy working today and not yesterday...is it possible that one of the prior user bans excluded one of the IP addresses of that anonymizer? Are you sure you used the same anonymizer both times?
The vbulletin logs should show what IP address you attempted to connect through yesterday when the post failed, and the address you just used to successfully post.
Be fearful when others are greedy, and greedy when others are fearful. Just another form of "buy low, sell high" for those who have trouble with things. This rule is not universal. Do not buy a 1973 Pinto because everyone else is afraid of it.