I created a very small setup (exe) and I can reproduce the "Error" Message Bug at the install process.
UAC is set to requireAdministrator but its happens also with highestAvailabke.
The Error does only appear if ALLUSERS is set to TRUE AND if the Version number has a specific number.
- Project A: Product version: 4.0.5 (ERROR MESSAGE)
- Project B: Product version: 10.0.0 (NO Error MESSAGE)
4.0.5 will result in 4.0.5.0 ! 4 digits separated by .
10.0.0 will result in 10.0.00 ! 3 digits separated by . and double zero at end
This is the only difference. It is strange but I am quality assurance specialist and that combination causes the problems !
We WILL buy an update if the latest version has fixed this bug !
Attached projects and setups...
Please look and help, because we must roll out the version and my boss is really angry

Thanks !