JOSM: changeset keeps uploading, never closes it

With larger changesets (>2000 nodes) Josm keeps uploading continiously for hours, although the changeset apparently is closed and uploaded after some minutes.
Is this a bug? I launch josm.jnlp (version 5531) from on a Windows Vista 32 bits computer.

I noticed there is a difference in opening and closing time of one hour + 7 seconds of a very small changeset. (84 nodes)
Aangemaakt op: zat 13 okt 2012 11:47:10 UTC
Gesloten op: zat 13 okt 2012 12:47:17 UTC

Could this maybe the cause in a mismatch between the time/date setting in JOSM and my computer that is causing this problem?

Edit: looks like a known bug:

Edit 2: It seems updating Java solved the time issue

Edit 3: Closing problem still exist with large uploads (4000 objects)

I’m not sure it’s related, but large changesets in JOSM in general are fragile - they do not automatically recover from a network or server problem.

Yes that could be the problem. See also
Guess I have to try not uploading too much data.