I tried installing subclipse through the "Help->Install New Software" and the URL is http://subclipse.tigris.org/update_1.8.x but it fails every time. It shows following items
  1. CollabNet Merge Client 3.0.8
  2. Subclipse (Required) 1.8.8
  3. Subversion Integration for Mylyn 3.x (Optional) 3.0.0
  4. Subversion Client Adapter (required) 1.8.2
  5. Subversion JavaHL
  6. Subversion Revision Graph

I tried them one by one and only the following could be installed, other four failed:
  1. Subversion Client Adapter (required) 1.8.2
  2. Subversion JavaHL

One of the errors I get is:

An error occurred while collecting items to be installed session context wasprofile=epp.package.php, phase=org.eclipse.equinox.internal.p2.engine.phases.Collect, operand=, action=). Comparison method violates its general contract!
My environment is as follows:

Is there anything I'm doing wrong?

I need at least Subclipse 1.8.8 and CollabNet Merge Client 3.0.8 also in addition to Subversion Client Adapter 1.8.2, Subversion JavaHL that I could install.