While trying to post an Invoice , getting an error as "Access key is not Valid"

Hi All,

I am trying to post an invoice . Don't no why it is throwing an error all of sudden .

Error is "Access Key is Not Valid".

As per the stack trace when I debugged , it is leading to the table (VendInvoiceInfoTable_W) and method (validateWrite())

Please find the below screen shot .  In the Image I have marked out the lines from where the error is coming from. I am unable to understand what is going wrong. I have also checked in the Table (VendInvoiceInfoTable_W) the AccessKey_BR field is blank for that particular PO. Is this causing issue ?

Please help me to understand the error and to clear it .

Regards,

Mania