I've gotten all the way through the Fortress of Regrets. Now I speak to my Mortality. And the dialogue ceases to continue as soon as he says
"Are they dead? Yes. Unlike you they have but one life."
"They wasted it for your sake"
At that point, there is no blue button in the bottom right corner to continue the dialog. Pressing nothing on the keyboard helps. The game is basically stuck there and I have to CTRL-ALT-DEL out.
ADDED: This problem seems to be related to the optional Subtitled Cutscenes feature included in Quinn's Fix Pack. When I removed it, the Transcendent One spoke those 2 lines in cutscene form, rather than dialogue-window form. And the rest of the dialogue proceeded normally. Looks like case closed.