When applying various hotfixes with Inventor 2012 SP1, the following error will result:
The reason for this error is because Inventor 2012 SP1 includes previously published hotfixes. Basically, you don't need them! In one of my recent cases, the user had Inventor 2012 SP1 and was trying to apply the Hotfix - iLogic assemblies:
I was able to confirm that this patch would work on Inventor 2012 and not on Inventor 2012 SP1. If you install the Product Design Suite, it automatically will download and install the Service Pack.
After the installation, you can go to the About Inventor to confirm that you have SP1 installed.
Some additional posts that refer to the Service Pack installation and hotfixes are also here:
Thanks to Warren Wetzel for confirming this solution.