Hey mate, do your private proxies pass the proxy test? My immediate inclination is to assume your getting a 407 error on your private proxies. Which means they need authentication. Your private proxy doesn't use a user name and pass it authenticates off your IP.
So you have to go into the your private proxy control panel and setup your ip to be allowed to access your proxies.
If they fail the proxy harvester, then try the new proxy harvester and when its done hit generate report and it will give you the error code as to why they failed. Its likely either the 407 or 404 or 403. If its 404 or 403 then you will need to contact Your private proxy, as they proxies are just down or you have them copied down wrong.
If they are passing the proxy test try running a portion of your list thru the blog analyzer and filter out all the ones that are bad/captch then post to those.
Ill bet its your authentication no setup in your private proxy control panel though. I think they have a tutorial when you login on how to do it. Video if I recall.