When I was I your server and setting up my second TaskChain, I tried to copy the pre- and post-conditions by selecting all of the boxes. When I do this by applying selected default values, I get a white screen. This occurs in my Moodle too. Sometimes it is nice copy down from before and then change a few things as necessary. Interestingly I set up post-conditions for task 1 and selected copy it for all of the tasks not only did it copy them, it also copied the pre-conditions even though I had not selected the pre-conditions column. No big deal, but does not seem to work completely correctly.