Hi, Eclipse uses SWT library (SWT uses gtk++ on linux). I think your problem is somehow related to SWT library running in KDE environment not finding gtk++ library. But this is just guess.
Try to download Eclipse from its site.
In my experence Linux distros are usually trying to be too smart with java apps, and I allways had better luck going to the source (Sun for JDK, Eclipse for the Eclipse).
I had also bad experiences with the packaged Eclipse from the distributors. They often patch Eclipse to have the plugins in the system and leave only the application in the users home. This gave me often problems with plugins because of the missing rights. Better to get a original Eclipse and place it in your home.
Mmh, you have the newest JRE installed (Sun JRE 6) so I cannot see a problem here. But you could remove the JRE package completely and reinstall it.
Do you have gcj installed? I think Eclipse still uses gcj, and doesn't work with OpenJDK. When I last used Eclipse in Fedora (KDE 4.1.8x and Fedora 10), it ran fine.