[otrs] problems attaching files after upgrade to 5

Hi, today we upgraded our installation to 5, everything goes smooth but now we can't attach files (not in notes or replies) the error we see when we try to upload the file is: [error] Apache2::RequestIO::read: (104) Connection reset by peer at /opt/otrs/Kernel/cpan-lib/CGI.pm line 1108 we noted also that with very small uploads (a few Kbytes) it works before upgrade (version 4) we never had any problem with attachments. Please help ! Thanks Marco