Ok, I managed to isolate the problem:Everything works fine as long as I'm putting \Tree [.$\sigma$ $\mu$ $ \mu$ ] into ERT. If I put it into a math environment (Instant Preview is turned "on") which I instantiated by pressing the "Insert Math" button the problem occurs as before.
How come?
Greets, Johannes -- Sometimes I lie awake at night, and ask, "Where have I gone wrong?"Then a voice says to me, "This is going to take more than one night." (Charlie Brown)
