When you are experiencing problems with your forum we would like you to do the following first:
1: Go to your accounts main controlpanel at: http://{forumurl}/acp -> Applications
and save the domain settings.

If still not working properly, reset the styles:
2: http://{forumurl}/acp -> Applications -> phpBB3 Configuracion -> phpBB3 Tools and reset the Styles.
(All the styles will then be resetted to the default one prosilver)

If you can't access your forums control panel go to
http://{forumurl}/acp -> Applications -> phpBB3 Configuracion -> phpBB3 Tools and reset the Modules.