YP-U1 strange Favorite problem

Seens Samsung doesnt have any MP3-player forum self, i take a chanche if someone here allso happens to own a Samsung YP-U1 player

http://www.samsung.com/my/products/audio/mp3player/yp_u1z.asp

Im experiencing problems with it, thath have just recentley occured for out of no-where
I can't longer add some tracks to favorites, its seems totaly random wich track is affected by this pre not

if i can mark one as favorite succefully, there is a chache thath the track just under is totaly un-mark-able, its doesnt happend anything when i press "enter"
i have Ogg-files added to my player, however there is both MP3:s & and Oggs thath have started to refuse being favorited, so its not format specific thath just Oggs are affected

cause some Mp3 files thath previously whas added favorites seem to have been auto-disbaled as favorites, and its inpossible to add them back again
i have tested to delete the tracks thath refuse, and add them again, but still its impossible to favorite them

the only thing i cant think of thath i have done recentley, is as i said, have added alot of Ogg-files overall to replace large sized MP3:s
but perhaps it can't handle larger quantity of oggs is some way? but why thath would affect previosly added tracks sounds wery unlogical
so i have no proff of this..im just trying to be informative, so dont buy my argument for nothing lol, cause i dont wanna quit using Oggs instead of MP3 based on a "perhaps" just

In settings there is a button "Deafult Settings" but it doesnt help after resett, perhaps i must delte all maps allsp? but i dont know if its worth it
i seem to have the latest firmware for my player allso

Im really confused, and i find all this wery unlogical

andy ideas, anyone head of anything similar?