piece of $#!t eclipse can't find the main class

At one point tonight Eclipse was working fine. After specifying a
separate output folder for class files (and losing all the files in that
folder w/o Eclipse giving me a chance to do anything with them; I hope i
never meet any of the eclipse developers because they may not live long
if I do) I can't get eclipse to build my application now. I always get
the lovely error:

java.lang.NoClassDefFoundError: org/rekkanoryo/ldapmgr/gui/LDAPMgr
Exception in thread "main"

I don't know why this is happening since that is the class that is found
when I tell eclipse to search for a main class (right click on
LDAPMgr.java, goto Run As, then Run to get Run dialog. I've specified
the following in the MANIFEST.MF file which is part of my project:

Manifest-Version: 1.0
Main-Class: org/rekkanoryo/ldapmgr/gui/LDAPMgr
Class-Path: lib/ldap.jar lib/ldapjdk.jar

I don't know where else I have to tell it the path to the main class
other than where I already have.

Any ideas on how I can teach eclipse to work again?

thanks