It's very strange..., I don't find anything on LimeWire's side that would indicate a 20,508KB limit.

There is a remote possibility of your provider being responsible because he doesn't allow any HTTP downloads requesting ranges beyond that kind of limit, however I have not yet heard of a provider doing that kind of thing.

We should watch that problem... possibly we may have to add some level of encryption to prevent your provider from doing that kind of thing if it really is your provider.