'Assets cannot associate with' QA error message when booking contract

Hi

I am getting the following QA error messgae when trying to validate a contract with an expense fee.

'Assets cannot associate with'

I completed the following steps to add a fee to my contract:

- Create Fee Line with a fee type of 'Expense'

 - Add Expense information such as Number of Periods, Amount per Period, and Frequency

 - Associate all assets to the fee using the Quick Apply Button.

When validating the contract I get the  error message.  What does this error message mean? Are you able to associate assets to an expense fee line?

Thanks

Kathleen