Hi Javier,
Enabling or rebuilding a package doesn't automatically increase its version number. In order to chage the version number that appears on the Guidace Package Manager when listing installed packages you will need to use the Version attribute of the <GuidancePackage> element in your package's manifest file, i.e:
<GuidancePackage xmlns="http://schemas.microsoft.com/pag/gax-core"
Name="YourPackageName"
Caption="YourPackageCaption"
BindingRecipe="BindingRecipe"
Description="YourPackageDescription"
Guid="c299bf43-9f62-4d0e-b5df-72feb3c0bf53"
Version="2.0"
And after modifying the Version attribute above you will need to do a full registration of your package (by running 'Register Package' recipe in GAT).
The important thing to note here is that GAX currently DOES NOT support versioning of packages, side-by-side running, etc.
HTH,
-Victor.