Yes if the avitars are not there, they will not load.
As for the skewing, this happens when the max upload size is set and avitars don't have dimentions stored in the database for them. Quite simply the fix is to either:
A. Remove them then add them back with the control panel.
B. Remove the maximum dimentions setting in the control panel (which is what they're defaulting to).
A will set the size of the graphics as they're entered.
B will make it so that they don't default to anything when there are no dimensions.
There is another option as well, and that would be to edit the template file for showflat.tpl and showthreaded.tpl to not use a size at all when including avatars (which I think should be the default option vs trying to set everything to a conformed standard; but, you can't make everyone happy).
