I think I need to come over and give you a run through . Are you playing on carpet? You may also be thinking that you are hitting the note and aren't, there's a fullllll strategy you have to get down and it's like picking up an instrument so it's a bit tricky at first.
Everyone's got their weakness, some people always feel that after stepping on a note that they have to put their feet back in the middle of the pad (which is HORRIBLE because after awhile as you get faster, it's impossible to hit every note doing this)
Some people can't hit the back button for shit.
Some people, i.e. myself, can't backstep . You aren't advanced enough to know what backstepping is yet, but let's just say I've been playing against my friend Timata for about a year now, I trained him from being a beginner up to heavy mode and HE can backstep like it's nothing, yet for some odd reason I CANNOT (in most instances, I get it every so often).
Your problem might be jumps (that's actually Timata's problem). I should come over and help ya out with it! Or at least make sure there's nothing wrong with your pad.
As for PS1 versions? You can, but they're harder and don't have many good songs on them. It's always nice to go back and revisit the classics, especially since that's where DDR first started (other than arcades), and you can pick up copies of the old games for cheap.