I've checked the sample app. It is based on outdated snapshots of RichFaces & Ajax4JSF. I've found out that the problem is fixed by replacing ajax4jsf-1.1.1-SNAPSHOT.jar with the latest version. We've introduced some changes there and the bug seems to be resolved.
We've also added workaround for commons-collections 2.x iterator chain bug to trunk.
Please check if the problem can still be seen on latest ajax4jsf & richfaces snapshots!