I figured out the correct work around - for anyone else having the same problem. I used Journal Entry to move the requisite amount of money from the Security Asset to Accounts Payable which requires a vendor name. Then, when I pulled up the bill under pay bills - the journal entry appeared as an option. I matched the journal entry to the bill and the balance of the bill was cleared, and the bill marked paid. So the solution is to use the Accounts Payable account so that the transfer of money is registered to the vendor who's bill needs paying.
