ok, going home from the office and not thinking about this helped. :)
i updated to the current CVS and it works now. so just ignore me for now, sorry.
Upgrade to a current nightly build (see sticky). If you seam-gen'd your project, run ./seam update-project, otherwise make sure to replace jboss-seam-*.jar and all of Seam's dependencies with the ones from the lib/ directory in your new build.
i already did that last night, it solved all the problems i was having with the data-table.