Hey Kyatric! Thanks for the reply, amigo.
I made sure FF was updated to 17.0.1, so that's not the case. Maybe it is something with the English version, but I don't know how to verify that one.
I re-made the ghost hunter tutorial game while learning C2 and added WASD movement as simulated 8-direction movement. Whether I preview it on Firefox or export it as HTML5 game, it bugs out--doesn't seem to matter how I do it. I know it's not Construct, as Chrome and IE9 execute the moving perfectly (though IE9 is sloooooow).
I'm trying to think of what else could be causing it as it doesn't seem this behavior was experienced by anyone else. I tried the 3 browsers on a desktop, laptop, and netbook with the same results.
Also, I'll check with Mozilla and see if I can get anything from there--thanks for the suggestion, Kyatric.
Is there any other way to simulate key presses in C2? Is it possible to map WASD to the arrow keys, so W corresponds to an 'UP' key press rather than 8-way movement, or is that the same thing?
Thanks again for your help, guys! I'm thoroughly impressed with Construct; it easily beats the other tools available for game-making.