Simeon,
Unfortunately you are using incompatible builds of Eclipse and MyEclipse (and also outdated). Please go to http://www.eclipse.org/downloads and download Eclipse 3.2 SDK and unzip it to a *new* directory, then go to our downloads area and download our 5.0.1 release and install that to a *new* directory as well, specifying your new install of Eclipse 3.2 when asked for it.
Then add -clean to the top of you eclipse.ini file, start it up, and open your existing workspace, you should be all set then.