Hi,
on my 2MB Edimax br-6104kp, i could not save changes permanently, because the image was too big. For me as an OpenWRT-Newbee it was hard to figure this out as the image seemed to run with no problems, and was with just 1,75MB smaller than my 2MB flash. But there was not enough space left for the jffs2-partition to work. An 1,5MB-image worked fine, I don't know where the threshould is.
There were no readable/useful errormessages for me as beginner. And the working midge-images are 1,8MB big!

Just to help other OpenWRT-beginners ;-)
bye