Not certain why this happens on devices only, but you should read in ccConfig.h for parameter CC_FIX_ARTIFACTS_BY_STRECHING_TEXEL. This in itself is a bad kludge, but it gives you a hint as to where to look.
Basically, you should make certain that all your positions are on an exact pixel boundary, ie on non-retina devices cast them to int, and on retina devices round to the nearest exact multiple of .5. Best way to ensure that is to make all your textures w,h even numbers ... the onus is on the artist for anything that will not move. If you move things, and the final position is calculated (for example in a ccTouches move,end), make certain you do this rounding there. Beware of batch nodes : the node itself, and all its children should be on pel boundary.