When two or more people are writting invoices you steal each others invoice numbers. Who ever saves first gets the number the other has to adjust everything that has the invoice number added to it eg; emails, job lists and paperwork. You dont know that your number has changed until you try to save. Small problem, simple fix.
Quick workaround while you wait to see if your proposed fix is implemented.
1) Click on the Customers menu and then Create Invoices
2) Before entering any items or making any changes, click the Save & New button so that your invoice number is 'saved'
3) Now at the top of the new invoice screen, click the Previous button
4) You will now be in the previously created invoice that has the saved invoice number and you can begin to enter the invoice line item details.
Regards,
Data Recovery Team