Strat frets choking

[willo]

Hey, on my new strat, it was all going so well until recently all the notes on all the strings below about the 8th fret have started choking and won't play/sound any kind of note. I've never owned a tremolo-equipped guitar so I'm at a bit of a loss as to what is going on here/how to fix it. I didn't alter anything about the guitar, although I did take the tremolo arm out of it's socket a few times - it's a floating trem, if that matters.

Anyway, if anyone's got any idea on what caused this problem and how I can rectify it, i'd be most grateful!

Cheers

[FELINEGUITARS]

Sounds like the truss rod is too tight

Has anything changed at all - different gauge of string?? Or change in tuning like tuning down??

Could be a combination of truss rod too tight and tremolo pulling back too much compared to where it was before bpoth of which could be caused by lightening up string gauge or detuning the guitar.

[willo]

Nah, I didn't change the strings since I got it. When I got it, it was set-up perfectly so frankly I'm baffled as to what's going on, here. I'm pretty sure I haven't detuned it, although I do sometimes let the strings slide out of tune and only tune them all to the E string (whatever note that's on), rather than perfect A440 pitch (if you see what I mean). I still am confused though!

Thanks for the suggestions!