Can't Get Phex to Start

I've installed Phex 0.7.3 and I can't get it to run.
This is the error I get when starting it from a command window:

java.lang.NoClassDefFoundError: org/xml/sax/SAXParseException
at phex.download.swarming.SwarmingManager.loadDownloa dList(Unknown Source)
at phex.MainFrame.<init>(Unknown Source)
at phex.gui.common.GUIRegistry.initialize(Unknown Source)
at phex.f.main(Unknown Source)

This is the command I used
java -jar phex.jar

I also tried running this batch file to include sax

set LASSPATH=.\phex.jar;D:\ant\lib\crimson.jar;D:\ant\ lib\jaxp.jar
java -jar -cp %CLASSPATH% phex.jar

Any help would be appreciated
Dave