unable to use proxies

[firehead]

Up until about a week ago I've been able to use various proxies without any problem. Now, whenever I put the check mark in Microsofts Explorer option box for using a proxy I can't view anything. I always get a 'page cannot be displayed' message. I've tried probably *0 to 20 different proxies from different proxy list web sites. I've tried it on different days too and nothing helps. As soon as I turn the proxy off by taking the check mark out of the box I'm able to surf. I've done everything I know to do. Might my ISP be responsible? Can they block someone from using a proxy?

[DATA]

HELO THERE,
IF THEY DECIDE TO LOOK FOR OPEN SOCKETS ON COMMAN PORTS such as *080 an 8080-yes if they can find open socket they can block access to it.
how ever if on the proxy *080 or 8080 are closed ports u may still able to connect through that proxy if u can connect to the proxy on some other port.