There are several I've noticed so far.
- Enc - Radiant Visasage line will not allow Jboots spell (and possibly any sow line)
- War - Arch Shielding on breastplate will not allow dru - Protection/Skin of/like Nature. You can cast Skin like Nature first and then Arch Shielding. Have not tested with enc.
- Dru - Nature's Renewal will not cast on anyone else - displays 'out of range' error