Doc,
Yes, the hotfix will not install if the software registry version is not 4.305.
I suspect from the output that you see, you have 4.3 and not 4.305. In order to apply the hotfix, you will have to install 4.305 (the latest distribution) and then apply the hotfix.
Our hotfix tools are pretty picky about applying changes to only very specific versions. In this case, 4.3 and 4.305 are functionally the same and have the same version number in the Help->About window (except for additional available translated languages), but the deployment tools won't allow this "4.305" hotfix to apply unless you've deployed the "4.305" distribution.
In the future, our hotfix tools are meant to be more flexible and allow a given hotfix to apply to different "versions".
In this case, there was only about a 4-week window when you might have been able to get 4.3 instead of 4.305. So this inconvenience will apply to the earliest adopters for 4.3 -- I hope that you don't feel we're punishing you for your enthusiasm...
Chris