FBX export error -- one mesh mapped to two UV maps

I am trying to export a mesh to FBX. The only unusual thing about it is that it has two materials mapped to two different UV maps. If I use FBX 7.4 binary, the export fails and I get a screen shot with a list of .py lines that failed (attached). If I use FBX 6.2 ASCII it exports but only has one material when I open it in Unity. Any suggestions? Thanks.