Packaging AS3 app for iOS

I have been using adt to package Air apps for iOS for over a year now without issue, then all of a sudden whenever I try to run it now I just get this:

Exception in thread “main” java.lang.AbstractMethodError: org.apache.xerces.dom.
DeferredElementImpl.getTextContent()Ljava/lang/String;
at com.adobe.air.Plist.parsePlistDictionary(Plist.java:388)
at com.adobe.air.Plist.newFromString(Plist.java:370)
at com.adobe.air.ipa.IPAOutputStream.GetResourceRulesOmitPatterns(IPAOut
putStream.java:129)
at com.adobe.air.ipa.IPAOutputStream.(IPAOutputStream.java:117)
at com.adobe.air.ipa.IPAPackager.(IPAPackager.java:65)
at com.adobe.air.ADT$Target.newPackager(ADT.java:261)
at com.adobe.air.ADT.newPackager(ADT.java:1872)
at com.adobe.air.ADT.getPackager(ADT.java:1877)
at com.adobe.air.ADT.getIPAPackager(ADT.java:1859)
at com.adobe.air.ADT.relaunchForIPAIfNecessary(ADT.java:372)
at com.adobe.air.ADT.detectTarget(ADT.java:736)
at com.adobe.air.ADT.parsePackage(ADT.java:682)
at com.adobe.air.ADT.parseArgsAndGo(ADT.java:603)
at com.adobe.air.ADT.run(ADT.java:446)
at com.adobe.air.ADT.main(ADT.java:496)

I’m on Windows 7.

Does anyone know the cause or how to resolve this?