Hey Dave,
Without seeing you lift, it's hard to say.
I'll take a guess that the 'arcing' you see relates to the timing and aggressiveness of the third pull (under the barbell and into the squat).
Regarding arm bend, you've probably seen it already, but part 2 of the Tommy Kono instructional video may be worth revisiting:
http://performancemenu.com/forum/showthread.php?t=416
btw, have you checked the USA Weightlifting site for a coach/club near you?