Are they failing to install? That way it would constantly be trying to install them each time, they wouldn;t be re-downloaded but attempting to be re-installed.
.Net Framework can be incredibly tempremental.
You can uninstall the offending Versions and install them again, This often fails however.
I've had a few machines do this and the best way I've found to deal with it is to rip out the whole .Net framework installed packages and install them again.
There was a tool written especially to do this. You will find it here.
It would be worthwhile to read through the page rather than just run the tool.