The Reporter is setting a connection timeout on the HttpClient, but wasn't setting a socket timeout. Currently the dash-collector site appears to be hanging responses to clients. Eventually HttpClient would give up but the enterLoop logic subtracted the processing time from INTERVAL. The resulting value was < 0, causing Thread.sleep to throw an exception.
The fix is to add a socket time out using HttpConnectionParams.setSoTimeout().
I've committed a fix for this http://github.com/raykrueger/dash-java/commit/7d606b19dbf9b28f9df855f835016a119379a2a8