Data transfer from timesheets to invoice not accurate

Data transfer from timesheets to invoice not accurate

I am having a serious problem with timesheets and invoices.  I have a project with a single task and single person billing hours.  I am required to submit a timesheet and an invoice to a customer.
 
Last week, I exported the hours for 3/16 - 3/31 to an xls file, and everything came through perfect.
 
When I hit the "create invoice" button from the exact same screen, and enter the exact same task/date information, it drops 8 hours off the total. 
 
Is anyone else having this problem with invoicing?
 
Thanks