Disappearing portlets after upgrade

Hi all,

I've faced some problem after upgrading Plone from 4.0 to 4.3.
When I click "Manage portlets" on a page in most cases I cannot see any already assigned portlets (although they are visible when I'm viewing the page. Even when I assign new portlet to that page it's not visible on a management page but it's displaying on the page in view mode...

Anyone maybe had that problem before?
I've checked logs and tried to debug the problem but no joy.

Thanks for all hints.