12.6 MessageBox

I'm working on some apps recently upgraded from PB 5 to PB 12.6 and use a recent copy of PFC.

The main app uses the RUN() function to execute several windowless PB apps. If the windowless apps try to use MessageBox, the message never appears. At first I thought it was nulls in the string being displayed but even hard coded messages don't appear.

Does anyone have any experience like this and know what can be done?

Thanks!