[OSM-newbies] joining two osm files (containing contours)

[J. Schneider]

Hello,
on my search about how to join two (or more) osm files of adjacent areas 
I found this
http://www.mail-archive.com/newbies@openstreetmap.org/msg01533.html
thread which clarified a lot. And after I inserted the --sort as stated 
in that e-mail I don't get the error message about unsorted content any 
more - but now I get:

org.openstreetmap.osmosis.core.pipeline.common.ActiveTaskManager 
waitForCompletion
SCHWERWIEGEND: Thread for task 1-rx failed
java.lang.LinkageError: loader (instance of 
org/codehaus/plexus/classworlds/realm/ClassRealm): attempted  duplicate 
class definition for name: 
"org/apache/xerces/jaxp/datatype/DatatypeFactoryImpl"
         at java.lang.ClassLoader.defineClass1(Native Method)

What I was attempting was: To combine two parts of contour lines in osm 
format. I had downloaded the SRTM4 data that is split in certain 
rectangles. My area of interest is contained in two neighbouring parts 
so I first extracted the interesting parts out of the original 
rectangles and then wanted to join them. (I hope I made myself clear.)

By the way: I am on windows, I use Osmosis 0.34.

any help appreciated.

Best regards
Joachim