I have a heavily Modded Oblivion install.
OBSE, FCOM, Better Cities, UL, Blah, Blah, Blah . . .
I also use Windows 7 Junctions to Link "Meshes", "Textures", "DistantLOD", and "BSAs" (A folder that contains about a third of my BSAs) over to a RAM Drive.
The default texture, meshes bsas were unpacked overwritten with QTP3 and RAEVD then split and repacked
All of the BSAs in the "BSAs" folder are renamed and registered in "Oblivion.ini"
Oblivion runs fine with hours and hours between crashes.

Whenever I try to start the construction set I get the error message
"Unable to Load CTL file" at startup.

The first thing I tried to do was
1) Backup my "data" and "My Games" directory to another drive
2) Delete oblivion completely
3) Reinstall with SI and latest Patch
4) Install Construction Set and Test (It works fine).
5) Restore Data Directory and Try to start Construction Set (It fails with the "Unable to Load CTL file" error)
6) Restore oblivion.ini file and try to start construction set (It failes with the "Unable to Load CTL file" error)

Before I start trying more complicated solutions, I was wondering if anyone has seen similar problems before or has any possible solutions I could try.

-dan

Since step 5 broke it, can we have more detail on how you did the "restore"? Did you delete the folder and copy another in to replace it? Merge the contents of a backup folder into the one you had? Something in that step overwrote or deleted a file that the CS needs, or changed its attributes to make it unusable. I forget which file "CTL file" refers to, but it's not oblivion.ini, which is only used by the game.

(Edit: CTL file may be a generic term for "file I consider important" - e.g. Oblivion.esm. There may be more than one candidate to check)

There's also the constructionset.ini - you could try simply deleting that to force the CS to recreate it... Same location as oblivion.ini.

I do wonder though, if the CS doesn't like Win 7 Junctions, even though the game doesn't mind.

Also check your DATA folder for a .tes file with the same name as your .esp - Sometimes if the CS has crashed you'll get one of these temporary files left behind that can cause this error - if you find one try renaming it to remove the .tes extension and try loading the .esp afterwards. (IIRC I had that happen once and removing the .tes file fixed it - but it's been awhile) - and this would make sense as to why reinstalling your old data folder made it stop working !

Yea I'll clarify that.
Step 5 expanded.
After getting the construction set to work on the new install of oblivion. I copied the data folder to a spare drive and then deleted the data folder.
Then I copied the "old" data folder back over and repaired all the Junctions.
Oblivion would of course not start up properly without the the old oblivion.ini file (with reference to all the BSAs) but I tried to start the CS anyway hoping for a different error at least.

I think the problem is one of the following things
1) the CS does not like transversing Junctions - This seems unlikely since they OS handles the junctions and because Oblivion has no problem with them.
2) the CS does not like how I repacked the BSAs. I have no idea why this would be seeing how the game handles them just fine
3) some other problem that i can't think of.

My current solution is to step through my install process testing the CS at each stage. That will probably take a couple hours though. I was hoping some else had a bright idea.

-dan

Also everything I can find on the web about the errors I am seeing

"Unable to load CTL File"
"Cannot load atmosphere model"
"Cannot load stars"
"Cannot load clouds"

Points to
1) oblivion not being installed
2) Oblivion not being patched to the latest version

Obviously oblivion has been installed and I have patched (and confirmed) to the latest version.

-dan

This messages appear too, if your cs-shortcut isn't set up correctly.
The paths must be:
X:\myDIR\TESConstructionSet.exe
and
X:\myDIR\

If the second path isn't correct or empty, the working-dir is false and this messages appear.

So I have two simple question: Did you exchange your cs-shortcut too? Or do you start the cs out of the directory?

Interesting.
I was initially trying to start the CS from wrye bash.
When that didn't work I tried to start the CS directly from the exe in the oblivion directly (installed on my setup at "C:\Oblivion\"
From step 3 on I was starting the CS directly from the oblivion directory.
Note after re-installing everything, the CS started just fine until I restored the data folder. Oblivion runs great, just not the CS

-dan

Check that the sArchive listings are the same in both Oblivion.ini and ConstructionSet.ini.
If you use a font replacer, check those as well.
I'm almost certain this is your problem. It's one I :brokencomputer: and :banghead: before.

ConstructionSet.ini ???
Wow I must be a noob. I didn't even know such a file existed . . . and how many mods have I released

thanks aellis. You just saved me a lot of headache

-dan