Cannot install Liferay IDE plugin - Comparison method violates its general contract

Question

We are considering using Liferay, so we decided to attempt to install the Liferay IDE. However it doesnt seem to work.

I am trying to install my Liferay IDE plugin as per this address:

http://www.liferay.com/de/documentation/liferay-portal/6.0/development/-/ai/installation

I have installed

Eclipse Java EE IDE for Web Developers.
Version: Helios Service Release 2

with Java JRE7.

This is the error I get when I go to the helios link :

http://releases.liferay.com/tools/ide/eclipse/helios/stable/

and select Liferay IDE

An internal error occurred during: "Install download1". Comparison method violates its general contract!

Answer 1

Helios' Update mechanism is not compatible with Java 7. Only Indigo SR2 and newer are. Either run Helios with Java 6 or use a newer version of Eclipse.