Excel COM Addin loads but the first Group in the Tab is missing

Hi:
I created an Excel COM Addin with Visual Studio 2010 (VB) for Excel 2007/2010 that implements a new TAB.
In my development computer and some other, the Addin works OK, but in several computers the TAB appears but the first GROUP of buttons is missing.
In Excel 2010, I can right click on the Ribbon, then uncheck and recheck my incomplete TAB, click OK and it now appears complete.
Excel 2007 does not allow this.

Any suggestions ???

MissingGroup.PNG
Thanks
Jaime