Threading and Net/Http (Mechanize)

Does anyone ever see alot of errors like this:
Exception `Net::HTTPBadResponse' at /usr/lib/ruby/1.8/net/http.rb:2022
- wrong status line: _SOME HTML CODE HERE_

When using threads and mechanize? I'm relatively certain that this is
some bad behavior between threads and the net/http library, but does
anyone have any advice as far as the upper limit of threads you want
to run at once when using mechanize/nethttp?