Eclipse - Subclipse - Unable to compare with Tag or Branch

I'm using Eclipse and Subclipse with my SVN repository. I'm trying to compare a tag I have checked out versus another tag so I select Compare With -> Branch (or Tag). In both instances I get the following errors:

"There are no tags for resource"
"There are no branches for resource"

Is there something in the Team preferences that I have to configure so that I can compare with other branches/tags?

Is your repository using teh standard directory structure?
/trunk
/tags
/branches

Also, are you able to view the history of a file in that project?

The answers to these will give more clues as to the problem.

We are using _trunk _tags and _branches as the folder names. I'm able to view the history on any of the files in the tags/branches I have checked out.

At what point do you get those errors? Right after clicking "Branch/Tag", or after filling out the "Compare with" dialog?
Also, which version of Eclipse and which version of subclipse?
I can do compares even among files that don't have trunk/branches/tags in their paths in Subversion.

I got it working. I had the wrong version of subclipse instsalled. We have SVN 1.6 so I needed to install this version:

http://subclipse.tigris.org/update_1.6.x

I had installed this one and it wasn't working properly:
http://subclipse.tigris.org/update_1.8.x

Download site: http://subclipse.tigris.org/servlets/ProjectProcess;jsessionid=59E3F12551957114E5CABB27F497A6E8?pageID=p4wYuA

Thanks for the assistance everyone it lead me down the right path to figure this out.

Yes, if you use multiple Subversion clients you must make sure that they are all at the same level, especially if using a 1.7 based client because how the .svn client database is created and managed changed dramatically in that version. (Not sure why subclipse went to version 1.8 for a Subversion 1.7 client, makes it quite confusing to keep things in sync.)