Redmine

Hello

When I'm trying to upload attachment redmine hangs for a few seconds and then prints "error" near the file name to be attached(please look at screenshot with Firebug enabled).

In console I got this message:
[2013-12-13 14:24:33] ERROR invalid body size.
[2013-12-13 14:24:33] ERROR HTTPRequest#fixup: WEBrick::HTTPStatus::BadRequest occured.

(production.log remains untouched)

I tried to do it with different browsers(Firefox, Chrome,Opera) but it behaves the same way.(of course tried to clean browsers' caches)

I had this problem with redmine-2.3 and now I've just run update to 2.4.1 and it's still the same.

# ruby script/about
Environment:
  Redmine version                2.4.1.stable
  Ruby version                   1.8.7-p352 (2011-06-30) [x86_64-linux]
  Rails version                  3.2.15
  Environment                    production
  Database adapter               MySQL
SCM:
  Subversion                     1.6.17
  Mercurial                      2.0.2
  Git                            1.7.9.5
  Filesystem
Redmine plugins:
  no plugin installed

Thanks in advance.