The two paned editor does not open on mac when using 64 bit version.

There is probably very valid reasons for this and the error message should actually explain why not just say "cant find plugin".

Add something like:
This error is most likely because of a problem with the native libraries.
If you are using a 64-bit version, try use the 32-bit version of Java or Eclipse instead.
If the problem persists consult the FAQ for possible other solutions.