Redmine

Hi all,
after upgrade from 3.2.0 to 3.3.1 I got this strange behaviour. See attached image.
Have you idea what happen ?

Many thanks
Alessandro

Information

Redmine 3.3.1.stable

Default administrator account changed
Attachments directory writable
Plugin assets directory writable (./public/plugin_assets)
RMagick available (optional)
ImageMagick convert available (optional)

Environment:
Redmine version 3.3.1.stable
Ruby version 2.2.4-p230 (2015-12-16) [x86_64-linux]
Rails version 4.2.7.1
Environment production
Database adapter PostgreSQL
SCM:
Subversion 1.6.11
Git 1.7.1
Filesystem
Redmine plugins:
redmine_my_page 0.1.9
redmine_mylyn_connector 2.8.2.stable
redmine_spent_time 3.1.2
redmine_subtasks_inherited_fields 1.1.0