In situations where there is a real need for security trusting your life on a free solution with all it's limitations seems a bit risky.
No proxies are really very good at all and they get blocked all the time as you probably know.
Plus they have issues with many web site features.
The number of proxies run by hackers is also growing daily and you risk your computer and more using one that claims to be anonymous.
The only proxy I've found to be somewhat useful because it changes IP's daily is http://www.wildtunnel.com.
It is a limited proxy and only works with a few sites. But it seems to work most times and is safe to use.
The better approach is the Personal VPN which unblocks everything, encrypts your entire connection for security, and doesn’t get blocked daily. http://www.surfbouncer.com