publishing iOS App error NullPointerException

Hi there,

i habe following problem: i am using Flash Builder 4.6 with adobe air 3.9.

i want to publish my app with flash builder and after instering the certificate and password,

an error occured:

Error occurred while packaging the application:

unexpected failure: null

java.lang.NullPointerException

          at com.adobe.png.PNGUtils.updatePNGMetadata(PNGUtils.java:60)

          at com.adobe.air.ipa.IPAOutputStream.addFile(IPAOutputStream.java:557)

          at com.adobe.air.ADTOutputStream.addFileFromStream(ADTOutputStream.java: 299)

          at com.adobe.air.ADTOutputStream.addFileFromStream(ADTOutputStream.java: 292)

          at com.adobe.air.ipa.IPAOutputStream.addSpecialIcon(IPAOutputStream.java :207)

          at com.adobe.air.ipa.IPAOutputStream.addFile(IPAOutputStream.java:185)

          at com.adobe.air.ApplicationPackager.createPackage(ApplicationPackager.j ava:71)

          at com.adobe.air.ipa.IPAPackager.createPackage(IPAPackager.java:217)

          at com.adobe.air.ADT.parseArgsAndGo(ADT.java:557)

          at com.adobe.air.ADT.run(ADT.java:414)

          at com.adobe.air.ADT.main(ADT.java:464)

i tried it with different adobe air versions, on another computer... the result is the same...

What can be the problem?

Thank you for your help,

Chris