Cannot choose client when creating a new invoice after upgrade

I am new to InvoicePlane. I just upgraded to InvoicePlane 1.4.6. When I create an invoice, the client field is already populated with the first customer in my database. The block for the customer is a read-only field and no longer a dropdown box. I have no customizations. I am using Apache 2.4.9, PHP 5.5.12 and MySQL 5.6.17. Please help!

I got the same issue after upgrading to 1.4.8
I think this issue is only on Firefox testing with Chrome all looks good.

As stated in the FAQ: please post your error logs. Without any logs nobody will be able to help and nobody will be able to fix any issues that may persist.