Can't get proxy to work
 

My ISP (Clearwire) "manages" port 6346. They haven't completely blocked it, but seem to be limiting my DLs. If I don't use LW for a while, I am able to DL a handful of files, then suddenly I'm back to nothing downloading. I can still search, but everything I try to DL just sits there until time passes-couple hours? So, I've been trying to configure the proxy setting.
I used an online proxy list, and tried several address/port combinations, with the HTTP proxy button checked, but LW just won't connect. If I go back to "no proxy", LW will connect again, but my usage is still restricted.
I know there were several working proxy addresses that I tried, because I also entered them into my network proxy config and was able to go online with nearly all of them.
What am I doing wrong?
I'm not even positive that the problem is with my ISP:
This slowdown just occurred in the past week, and someone told me that they contacted Limewire and were told they've been having server trouble, but I don't see a single mention of any problems in the forums.
I see some people say they are having problems related to Quicktime 7.0.4. I just installed it a few hours ago, and I don't see any difference.