Eclipse : Java Developers Edition

Hi all,
Recently I found a trouble as you can notice from the heading. Please give a solution to solve this error.
Please help.
Thanks.
Platform
Operating System: Ubuntu 12.04
Eclipse: Java Developer version, Indigo SR2
Hibernate-tools: 3.4.x for Indigo (I download it from the Marketplace)
When I try to install the Hibernate-Tools and use content assist, I get the following errors:

Problems During Content Assist
Moreover, when I perform something related to dialog, then Eclipse shows the following dialog:

Problem Occurred
