Problems with NoClassDefFoundError

Hi!
I do have had some serious problems with NoClassDefFoundError during Launch in Eclipse
I have now found a manual solution, but I like to know if someone have had the very same problems and if, how they were solved.

Due to documentation should you add external archives to your project like:
Right click the actual project
Build Path
Add External Archives
Choose ‘any_jar’.jar and OK

If there are any problems during runtime to find these jars do like:
Run
Run Configuration
Tab Plug-Ins
Add Required Plug-ins

It’s also possible to add jars like:
Right click the actual project
Build Path
Configure Build Path
Tab Libraries
Add External Jars…

It should then be possible to see the attached jar’s in the .classpath file for it’s project
I’m not convinced that it always is like that?

So the solution I have found, which also work, is like:
Make a new folder ex. lib in project.
Paste and copy to folder lib the very same external ‘any_name’.jar as abow
In MANIFEST.MF add to Bundle-ClassPath:.,
lib/‘any_name’.jar

This is confusing and I just like to know if someone else have had the very same problem, an maybe found out some other solution?

Regards Örjan