If your foreign taxes are over $600 then you don't always get all your withheld tax back. Your overall tax rate has to be 15% or higher to get it all back. Otherwise the amount you get back is prorated depending on your overall percentage US tax.
If I am wrong, by all means jump down my throat and tell me.
If your foreign taxes are over $600 than you must fill out form 1106(?) to get credit at all for your foreign paid taxes.