When adding a control to a form add it to the end of the tab order.
Add four labels to a form by double clicking on the label in the tools.
Check the tab order. It appears to be random tab order. (label3, labal4, label1, label2)
When building a form, in most cases, I build controls in order (unless I forget one).
Also on the tab order allow selection of multiple controls to be reordered as a group
Thanks Brian - I remember this issue being raised before. I have logged it now and will implement it in FF4.