Error adding table borders in Arbortext Editor 7

Good morning Arbortexters,

After upgrading to Arbortext Editor 7, I'm getting the following message when adding borders to a table, and the borders are not applied correctly.  We use a custom Fosi, so I'm not sure why there's a reference to the dflt.fos in this error.  We've made no recent Fosi or DTD changes, and using that same DTD and Fosi, I can add table borders with Arbortext 5. Does anyone know how I can resolve this error?

Thanks!