mysql not giving result

i have this SELECT query that it doesn't show any result.. it is very inconsistent, it works with other fields but it doesn't with others... and the sad part is, it doesn't give any error msgs. i don't if my other database is growing rapidly(i have more than 400 tables) causes this. i'll give you the genearated sql statement: >>>>>>>>>>>>>>>>>>>>>>>>. SELECT products.id,products.itemname,products.fullpic, products.ourprice, products.otherprice, products.description, products.ingredients,products.featspecs, products.export, products.lent, products.width, products.height, dim_unit.abbr, products.weight, wt_unit.abbr, manufacturer.name, products.datemanuf, products.country, products.order_inst FROM products, dim_unit, wt_unit, manufacturer WHERE products.id='11' AND dim_unit.id=products.dimunit AND wt_unit.id=products.wtunit AND manufacturer.id=products.manufacturer >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> thanks so much for the help, Brian Feliciano