Nervt mich auch 
Hier die Fehlermeldung samt Stack Trace
POST http://www.openstreetmap.org/api/0.6/changeset/4896214/upload... org.openstreetmap.josm.io.OsmTransferException: java.io.IOException: Error writing to server
at org.openstreetmap.josm.io.OsmApi.sendRequest(OsmApi.java:608)
at org.openstreetmap.josm.io.OsmApi.sendRequest(OsmApi.java:476)
at org.openstreetmap.josm.io.OsmApi.uploadDiff(OsmApi.java:426)
at org.openstreetmap.josm.io.OsmServerWriter.uploadChangesAsDiffUpload(OsmServerWriter.java:123)
at org.openstreetmap.josm.io.OsmServerWriter.uploadOsm(OsmServerWriter.java:199)
at org.openstreetmap.josm.gui.io.UploadPrimitivesTask.realRun(UploadPrimitivesTask.java:237)
at org.openstreetmap.josm.gui.PleaseWaitRunnable.doRealRun(PleaseWaitRunnable.java:83)
at org.openstreetmap.josm.gui.PleaseWaitRunnable.run(PleaseWaitRunnable.java:129)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source) Caused by: java.io.IOException: Error writing to server
at sun.net.www.protocol.http.HttpURLConnection.writeRequests(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.writeRequests(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at java.net.HttpURLConnection.getResponseCode(Unknown Source)
at java.net.HttpURLConnection.getResponseMessage(Unknown Source)
at org.openstreetmap.josm.io.OsmApi.sendRequest(OsmApi.java:532)
... 10 more