http://download.eclipse.org/technology/m2e/releases install error

Can you try running Eclipse as Admin and try this again?. Let me know how that goes.

what is the update url are you using, is this it m2eclipse.sonatype.org/sites/m2e ?

Edit:

There are incompltibilities with different vertions of Eclipse and plugins,

I suggest you to use the update site

http://download.eclipse.org/technology/m2e/milestones/1.0

OR

http://download.eclipse.org/technology/m2e/releases

The best bet is the release version, But if you are still getting the issue, try the milestone 1.