Entering budgets against departments in Chart of Accounts

I've come across a strange situation when entering budgets.  I have about a dozen departments and have gone through the revenue and expense accounts specifying which departments can be posted to each GL account.  Now I am entering budgets.  I have found for several GL accounts that although I have specified the Admin department (1000) as an allowable department to post to it will not show up as an available department to enter a budget against.  There seems to be no rhyme or reason as to which accounts allow the Admin department to have a budget.  This is a major inconvenience for me.  Any ideas?