The Run cycle Animation's strobing like a mother licker. you're making the classic mistake of taking the exact same leg (and arm) loop and offsetting them in time but not in space. The only thing that differentiates the front and rear leg (and arm) is shade and tone... but this in the wrong way to do it. Regardless of shade and tone the shape is identical, regardless of what is happening within the space taken up but the pixels... Convert the image to a silhoette... this is what I'm seeing... with the exception of a few unique pixels on the hair a couple of frames offset in the Y by a pixel what you have is a 5 frame loop...
You could try;
1. Try offsetting the arms/leg loops in the X by a pixel or two...it would require a slight remodel of the torso to make the character face slightly towards the viewer...
If you insist on a side on profile view;
2. An odd number of frames count is the one way to avoid strobe... or making each frame unique... in terms of a run cycle it would mean that the opposite leg would be placed in a position that wouldn't visually synch up with it's opposite... (if that makes sense) - essentially you need to animate on 3's not 2's - (to use dope sheet terminology) - here's a couple of example anims I've jsut knocked up to try and illustrate this...

This first rotating box, is animated on 2's - it's 4 four frames and revolves 1/2 turn but ... this strobes quite violently... mainly because it's essentially just 2 frames... a diamond, and a square - that's all the eye is seeing, however, the internal sections give the impression of a full rotation because of the blue and white sections.
Now look at this...

This is animated on 3's - it's 1 additional frame above the previous example at 5 frames and also rotates 1/2 a turn... it strobes also but reads better as a spinning square because the eye interprets the form differently and therefor it reads better.
And here's a couple more, but circles this time.
in twos...

and in threes...
Anyway... that asides I've had a good look at that run cycles and, well... you've got inconsistent masses... the leg distorts quite a lot from frame to frame... the length of the calf shifts quite a lot ... :S - sorry...
I've taken the liberty to have a fiddle... Here you go:

Starting from top left, your original anim. Then there's that silohette I was on about...
The next sequence is your original with what I've placed over the top to be - hip, knee and heel, notice how the green lines in between extend and contract... and (you to look closely at this) the thigh jitters forwards and backwards on one frame... you need to try and get these moving in nice smooth arcs...
look here for more info on arcs [and constructing walk loops]The next sequence along is the silohette with a more fluid line construct (hip, knee, heel) keeping a mind on consistent lengths etc.
Moving downscreen, there's 3 single stick legs animating: the top two are identical (except color) these are then overlayed (to the right), to show that they strobe... (because they're identical), directly below that is the same legs offset slightly in the Y to demonstrate how identical legs can still work and not strobe.
Finally, there's the other lone leg (with the green line under it) this one is a unique loop, based on your original... I've overlaid this with the initial leg, directly over each other (no Y offset) to illustrate my point earlier...?!?!
Phew... I'm tired after that...
PS. the jumps nice... (except the arms don't read too well when they're up... [think of the silhoette it needs to read without detail])
enough!
Keep on pushing!