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.
at com.adobe.air.Plist.parsePlistDictionary(
at com.adobe.air.Plist.newFromString(
at com.adobe.air.ipa.IPAOutputStream.GetResourceRulesOmitPatterns(IPAOut
at com.adobe.air.ipa.IPAOutputStream.(
at com.adobe.air.ipa.IPAPackager.(
at com.adobe.air.ADT$Target.newPackager(
at com.adobe.air.ADT.newPackager(
at com.adobe.air.ADT.getPackager(
at com.adobe.air.ADT.getIPAPackager(
at com.adobe.air.ADT.relaunchForIPAIfNecessary(
at com.adobe.air.ADT.detectTarget(
at com.adobe.air.ADT.parsePackage(
at com.adobe.air.ADT.parseArgsAndGo(
at com.adobe.air.ADT.main(

I’m on Windows 7.

Does anyone know the cause or how to resolve this?