View the "tab order". Scroll down the lsit until you find the field that lies closest to the top left of your form. Drag that field to the top of your tab order list. Save and close the form. That should do it.
The tab order is the default order that your cursor will use to jump around the various fileds onscreen if you use Tab or Enter. When you're designing forms, mving stuff round, adding new stuff, it's gets all messed up so use this list to put things back in the correct order.
