OptOnline and other ISPs belonging to CableVision are known to
block Gnutella. They don't to this everywhere and everytime.
This is either because of technical problems on their site
or to confuse their users. The only reliable way is using
encrypted connections but LimeWire still doesn't support
this.

You should however really tell your ISP to cut the crap
and cancel your account. According to US laws what they are
doing is _illegal_. They will lose their "common carrier"
status because of this very soon.