Are you using different versions of Acrobat/Reader?
I using Acrobat 8 to edit my forms. I opened one of my forms and looked at the "Form Properties" it says...
Form Type: Acrobat 6 (Static) PDF Form
Text Formatting: Version 7
Event Model: Version 7
I also use Adobe Reader 9.
I emailed one of my own forms to myself and opened it with Adobe Reader 9 and saw the same problem.
If I open the form back up in Adobe 8 then my tabbing order looks just fine.
There were issues with the tabbing order between all of those versions. You may wantt o try changing the target version to 8.1 and see if that makes a difference.
Thank you so much for all your input. You were absolutely correct about
there possibly being a conflict with the Adobe versions. For the most part
I've cleared up the problem. Now I'm told the tabbing order gets out of
sequence if there is a "check box".