"Please enter a valid cost center" while creating expense report.

Hello Everyone,

Our business is contemplating to move to iExpense. I am doing a demo for the same purpose to business on our DEV instance.
If all goes well during the demo, business might decide to go with iExpense.
When preparing the demo, I am getting the weird issue. Once I click on Create Expense repot, it allows me to go to the next page.
But while saving the record, I am getting the following message

"Please enter a valid cost center".

When searched for it in Google and Metalink, I am getting the common solution, but that does not apply to our situation.