I checked my profile since the board software has been changed. I made two edits, one to my email address and the other to the 'Topics Per Page' setting - now set at 50. When I returned to 'All Topics' (after entering my new password) the threads were in reverse chronological order. I went back to my profile, changed the thread order to 'reverse chronological' and now it's back to normal.
Also, the conversion changed the open and closed brackets in the bold command in my signature to left and right arrows. I've already changed them back but thought you might want to know about it.