When i try to insert 2.5.7 with dependencies jar into projects i have " Conversion to Dalvik format failed with error 1" message and i have to remove library to continue building. i'm using Version: 10.0.1.v201103111512-110841 Davlik Debugger and Version: 1.3.2.20110218-0812 eclipse ide.
Have a look at http://code.google.com/p/ksoap2-android/