I remember getting a .reg file from Trimble’s website that enables Sketchup to save to network locations. I can’t find it anymore but here are its contents:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System]
“EnableLinkedConnections”=dword:00000001
Save this to a file with the extension .reg Double click on it to add the values to the registry and you should not get this error any more. It worked for me.
to fix this problem i just disable my antivirus or uninstall them and its work again to save file
Same thing with new Kaspersky Total Security. Exclusions did not solve the problem. Only uninstalling helps.
I too had to uninstall Kaspersky Security Cloud Free and reactivate Windows Defender to allow Sketchup 2017 to autosave or save manually.
I reported this problem for Kaspersky. They found the issue and told me to wait for new version of kaspersky antivirus 
And they cannot say when, it will be released.
After 6 months there is still no new version of Kaspersky Antivirus.
I spoke too soon!
Same problem again today, with Windows Defender.
[Edit]
I have now made an exception for the Sketchup 17 program file in Windows Defender and it seems to be working.
Windows Key with ‘I’ (to open Settings in Windows 10)
Type ‘Virus’ in the box and click on ‘Virus and threat protection’
Click on ‘manage settings’ under ‘Virus and threat protection settings’
scroll down to ‘Exclusions’ and click on ‘Add or remove exclusions’
click on ‘+ Add an exclusion’
choose ‘file’
navigate the tree to 'C:\Program Files\SketchUp\SketchUp 2017'
choose ‘SketchUp.exe’
I have had the “exception” error forever. It is directly linked to Podium. I found in frustrating at first, now simply annoying - but simply because when the notification occurs I am always mildly startled (you know - that sinking feeling when you computer tells you there is something wrong, and you wonder how bad?) Not too long after it first occurred I discovered the conflict with Podium, and that the file was still saved but in a different location - just as auto backup is. Apart from my psychological issues, I don’t consider this to be a major problem, and simply rename the save as I do with autosaves if required. Not having programmer smarts in this area, I never dug deeper, but guessed there is a file locking sort of conflict - and from this conversation, that has something in common between the other programs, etc, and SU.
I too get the same problem (CFileException 0 when saving a file). I saw that TheGuz states with one user this was to do with AntiVirus software. I am using Norton 360 and when I switch this off temporarily and tried again, the error does not happen!
So why not add SketchUp to the ‘exceptions’ list in your AntiVirus settings ??
I too use Norton 360 and I have never seen this, and I haven’t changed any settings.
Are you saving to a special folder, like one that syncs with a cloud storage like Dropbox or Google Drive? Or are you running plugins like the ones mentioned in the previous posts?
I still get this when I try to save after exporting to Kerkythea. It appears that the exporter isn’t letting go of the SketchUp file after the export. This is the only time I get it and since I know what causes it, I just save before exporting. If I save afterward I just wind up with an additional copy of the file.
I used to get “CFileException 0” all the time with my own CutMaster.exe file
Since CutMaster is Windows only I switched the code an now I do not get the exception.
where filename is the full path to “cutmaster.exe” and rpt_name is the name of the csv file that I am passing over to CutMaster.
pid = spawn(“"#{filename}" "#{rpt_name}"”)
win_shell = WIN32OLE.new(“WScript.Shell”)
win_shell.Run(“"#{filename}" "#{rpt_name}"”)
So spawn is out and win32ole is in.
The problem is Sketchup spawns a process and then when saving (or auto saving) Sketchup won’t let go of the spawned application and won’t properly save if the spawned application is still open.
I tried getting Trimble’s attention to this - but to no avail.
sounds like this could be solved by having a separate thread for all file operations… which also would allow to advertise with multi-threading support 
I just started getting this error code: “CFileException 0” When trying to save a file in Sketchup 2021. I discovered this is caused by running the new V-Ray Vision window because it creates a live link to V-Ray. I closed the V-Ray Vision window and the error went away. FYI
This detail for Windows10/Sketchup and Defender was very helpful. Thank you for being so detailed and specific. Much appreciated.
I consistently received the CFileException 0 error. By turning off Malwarebytes antivirus, the problem went away.
Hope you have some other antivirus package running.
Same issue. Makes V-ray vision useless, since the idea behind real time linking is that you can actually work on your file and have a render engine open.
I have the same problem recently, the only new aspect is that I have installed SketchUp 2025 !
Yes, I work on my Dropbox Desktop folder, but I never had any problem with that befor. I do not have Malwarebytes installed on my computer. Really frustrating ! On my side, it happen when I work on Layout, make changes on SketchUp and then try to save to update Layout after, it use do be very usefull and worked fine until now.