Eclipse Installation Error : Missing requirement: EasyXtext UI 1.0.15

[quentinsup]

The plugin installation fails when trying to resolve xText dependencies.
It is no longer working since months (but was working very well before).

I'm working with Kepler but i've tried with different version of Eclipse with the same issue.

Cannot complete the install because one or more required items could not be found.
  Software being installed: LESS 1.0.22 (net.vtst.ow.eclipse.less.feature.feature.group 1.0.22)
  Missing requirement: EasyXtext UI 1.0.15 (net.vtst.eclipse.easyxtext.ui 1.0.15) requires 'bundle org.eclipse.xtext.ui 2.7.2' but it could not be found
  Cannot satisfy dependency:
    From: LESS 1.0.22 (net.vtst.ow.eclipse.less.feature.feature.group 1.0.22)
    To: net.vtst.eclipse.easyxtext.ui [1.0.15]