I have changed to "LogLevel debug", but there are no additional helpful entries in the error.log:Did you use loglevel debug in your test server? I would hope that at level debug you should get some log message what went wrong.I will check that entries asap.
[Mon Jun 11 21:41:39 2012] [notice] Apache/2.2.16 (Debian) PHP/5.3.13-1~dotdeb.0 with Suhosin-Patch configured -- resuming normal operations
[Mon Jun 11 21:41:39 2012] [info] Server built: Apr 1 2012 07:14:38[Mon Jun 11 21:41:39 2012] [debug] prefork.c(1013): AcceptMutex: sysvsem (default: sysvsem) [Tue Jun 12 19:30:40 2012] [error] [client 79.210.52.151] request failed: error reading the headers [Tue Jun 12 19:58:29 2012] [info] removed PID file /var/run/apache2.pid (pid=16308)
[Tue Jun 12 19:58:29 2012] [notice] caught SIGTERM, shutting down access.log:79.210.52.151 - - [12/Jun/2012:19:28:58 +0200] "POST /upload.php HTTP/1.1" 200 373 "http://uploadtest.puzzleandplay.de/xxx.php"; "Mozilla/5.0 (Windows NT 6.1; rv:13.0) Gecko/20100101 Firefox/13.0" 79.210.52.151 - - [12/Jun/2012:19:30:19 +0200] "POST /upload.php HTTP/1.1" 400 493 "-" "Mozilla/5.0 (Windows NT 6.1; rv:13.0) Gecko/20100101 Firefox/13.0"
The first upload (at 19:28:58) of a 475K large file was successful. The second (at 19:30:19) of a 480K large file failed with "bad request". Here you can also see the difference of 21 seconds from the incoming of the request (at 19:30:19) and logging the error (at 19:30:40).