I downloaded some packages from the packman repository, these are gstreamer plugins, and when I try to install them yast display a message, Not installable provider, conflic resolution, change the provider and I have the chance to select the package from packman, and it allow the installation, the question is, What does it means?, I am using Open Suse 11.
It means that the packages you try to install require other packages which yast cannot find, so there is no installable provider for the missing packages. Do not download packages but install them directly from the repository.
Actually YaST can find the packages but from a different provider (i.e. simplifying, a different repository) hence the Change provider message.
Notice the package might be in the same repository YaST expected to find it, but with a different version. A newer version of the package is what is required by the updated package and that one can be found in the other repository… uhm, makes sense? 
yes I downloaded some packages from the packman repo and some were found with rpb.pbone.net but I don’t remember which ones, I am creating a collection of packages that can be installed without internet, this is not a missing dependecies error, it says that the package exits but it is not a installable provider and give you the option to change the package, the question is, is it safe to install these packages? the problem is that not all are availables in the same repository
The answer would be yes, it’s safe as long as you install them from repositories you trust.