I was having an issue installing .net 4.0 on my WSUS server. I was receiving an 8024800c error. Reboot solved nothing.

I ended up stopping the automatic updates, deleting the SoftwareDistribution folder, restarting the updates service, and then I was able to install.

Open a command prompt
net stop "Windows Update"
del C:\Windows\softwareDistribution
y
net start "windows update"
Re-run your installation