Print preview problem

Hello, we have a strange little problem: we set a global (text) to some text like ‘July 2004’ and use it on a label in the header of a report. In browse mode everything is fine, but in preview we get an empty error that throws the following in the log:

java.lang.NullPointerException
at com.servoy.j2db.dataprocessing.x.containsCalculation(Unknown Source)
at com.servoy.j2db.dataprocessing.ak.getValue(Unknown Source)
at com.servoy.j2db.dataprocessing.am.setRecord(Unknown Source)
at com.servoy.j2db.dataprocessing.d.a(Unknown Source)
at com.servoy.j2db.a.i.if(Unknown Source)
at com.servoy.j2db.a.i.(Unknown Source)
at com.servoy.j2db.a.g.a(Unknown Source)
at com.servoy.j2db.a.e.for(Unknown Source)
at com.servoy.j2db.a.b$1.run(Unknown Source)
at com.servoy.j2db.util.ar.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

This does not happen when the global contains for example ‘July 2003’?!

Thanks.