Tashia had Spell Trap active right before entering Spellhold for the first time. After the Irenicus talk, the Bhaal encounter dream, and the Bodhi talk, when I finally regained control of my party, Tashia was there (green circle) but wasn't selectable at all. Tried various things: talking, removing her and getting her to join again, but nothing worked. I had to go back to the autosave and clear the spelltrap (Ctrl-R), which fortunately solved the problem.
Just something to watch out for
I apologize if this has been reported before.
-Kaitsuburi
PS. I am romancing Tashia, and I don't have the Cut-Scenes from Weimer's Ease-Of-Use installed.