XMLport output of boolean changed after technical upgrade 4.0 SP 3> 5.0 SP1

Hi all,
Yesterday we've performed a technical upgrade of Navision 4.0 SP3 to Navision 5.0 SP1. Everything went OK. This morning however I got a call that the XMLexport to some program no longer worked.
If I connect to the database with our 4.0 client it works fine again. I found that elements in the XMLport that are filled by Booleans were 0 or 1 in the XML file from the 4.0 client and are now False of True. The program that imports the XML only works with False or True.
I can't find wether this is a setting that can be changed or something, but we would like to have our 0 and 1 back.
Does anybody know how to fix this?
Thanks in advance