.Net 3.5 Fails Online and Offline

There are dozens of posts here about .Net Framework 3.5 failing to install. Several solutions have been proposed, that work for some people but not all. None work for me.

I won't repeat what others have already posted, but here very briefly is what I've tried:

• installing from Control Panel > Programs and Features ("online install")
• offline install via DISM
• third party utilities that provide an interface for DISM, hoping to prevent typing errors
• copying the /sources/sxs to the C: drive and trying all the above again.

What I have not done is refreshing, resetting or reinstalling. I've put too much work into setting up Windows 8.

There is one constant in every attempt: the returned error code is 0x800F0922. However, I cannot find an explanation for this error code. Every reference I have found to this error code doesn't explain the error code, but instead provides one of the solutions for installing .net 3.5 which I've already tried.

I am now at a dead end. I cannot install .net 3.5 by any method posted here, and I cannot find an explanation for why I cannot install. I think my best, last course of action is to somehow find out the meaning of 0x800F0922 and hopefully figure out what is going wrong. Can anyone help?

EDIT - Here is an excerpt from my DISM log (with emphasis added):

Encountered the option "featurename" with value "NetFX3"
Encountered an unknown option "featurename" with value "NetFX3"
Encountered the option "source" with value "D:\sources\sxs"
Encountered an unknown option "source" with value "D:\sources\sxs"
Initiating Changes on Package with values: 5, 7
CBS session options=0x20100!
Error in operation: (null) (CBS HRESULT=0x800f0922)
Failed finalizing changes. - CDISMPackageManager::Internal_Finalize(hr:0x800f0922)

Hope this helps.

You may have done this since you say you have used the Programs and Features panel. But if you look at Turn Windows Features on or off, there is an entry for .Net 3.5. Is that how you are trying to install?