Need help with n-back task on Direct RT v.2006

Hello,
I am trying to set up the n-back task and am having issues with the min-max values. In this task I have letters being displayed for 500ms, and blank screens in between each letter for 1500ms. After every third letter (the third letter serves as a target letter) the subject will either press the s button to indicate that this letter was the same one that was displayed two trials prior or the d button to indicate that the letter is different from the one that was displayed two trials prior. After this third letter, there will be a blank screen for 1500ms and during these 1500ms participants will press the s or d button (currently in the file I attached these screens are not blank, but have the trial number. there are 45 trials.). The problem I am running into is having constraints on both the time in which participants have to respond and what buttons they can press. I have tried using 0-1500! in one of the time columns and rt:32,31 in the other time column, but in this case the min-max value is ignored. I have also tried using 1500 in one of the time columns and rt:32,31,-1 in the other time column, but in this case the 1500ms is ignored and no data is recorded except for -1 for every single trial. I've also tried putting 0-1500!;rt:32,31 in one single time column, but once again either the ms constraint is ignored. I've also noticed that when I use the 0-1500! time and rt:32,31, my stimuli will not be displayed on the screen at all. When I use 1500 and rt:32,31 the ms constraint is ignored and the program waits until i press either the s button or the d button. When I use 1500 and rt:32,31,-1, the stimulus will flash very quickly on the screen, which indicates that the 1500 time constraint is being ignored in this case as well. I have version 2006.2.0.28, and according to the direct rt user manual, this version solved some previous issues with the -1 keycode, but I am still having the problems that this version was intended to fix. I am also trying to set up practice trials at the beginning, in which users are given feedback on their accuracy and speed, in which case I am attempting to use jump commands. The jump commands seem to work fine, but I am still having the same issues whether I am using the jump commands or not (it doesn't seem to help if i remove them). I've attached the zip-file containing the files I have been working on. Your help would be greatly appreciated!