products disappear from web page

[Momir]

joomla 2.5.4 WM 2.0.6

i have shop working and that sudenly without instalation of any upgrades all products disappear from web shop (front page). the products are stil visible in administrator interface and they are publish. i unpublished and published them again and nothing hapens. then i have cloned products and these new products appear in the shop immediately. this hapened 3 times already and i do not know what is the problem and when will it happen again.
any solution?