Just wanted to add my voice to the chorus here… been experiencing the same freezing issues, lag, and bombing out of the mission as the others… but it happens at different stages of the scenario… I thought it was related to prime time usage, but is been the same problem whether i log in during prime time, or late at night.
I have not experienced any of these problems elsewhere in the game.
FWIW, my toon is a lvl 49 Norn Mesmer.