System error 6 The handle is invalid on Net Use

The user has a 3-user network, all on Win7 Pro, One PC is where they share their files, with a computer name of "Server".  Up until today, the two workstations were mapped to the Server PC using this command:

Net Use F: \\server\c  

This has worked fine for years.  But today they can no longer connect.  If I delete the F: drive mapping, and once again do Net Use F: \\Server\c I get this error:

System error 6 has occurred
The handle is invalid

And if I browse to Network, I can see the PC named Server, but if I double click it I get this error:

Windows cannot access SERVER
Check the spelling....etc....
Details: Error code 0x80070033
The network path was not found

Other details:

1) They use Norton security.  I have tried turning off the firewall and antivirus on a workstation and on the server to no avail.

2) I can still do the normal Net Use mapping on the "Server" computer--but not on the other two PCs.

3) I went to do a system restore on the Server PC, but to my surprise Windows said was disabled--so no help there.

Any ideas?  TIA
LVL 3
sasllcAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

sasllcAuthor Commented:
In the last few minutes two more customers have called in with the same problem--for the first time ever.  I wonder if there was a Tuesday night update to Win7 that is causing this??
Iamthecreator OMIT Admin/EE Solution GuideCommented:

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
sarabandeCommented:
Net Use F: \\server\c

can you check whether there is still a share named C at Server ?

anyway, you may think of using C$ as share name or - even better - use a much longer and less easy guessable name with a $-suffix. the $ makes the name invisible in the network for clients with their windows explorer.

Sara
sarabandeCommented:
KB4480970

iamthecreator is right. i also got a message that the update KB4480970 deactivates the Network Controller on Windows 7 and Server 2008 systems such that shares at a server are no longer accessible.

You have to uninstall the package for example by the command

   wusa.exe /uninstall /kb:4480970

at the command line and reboot.

Sara
sasllcAuthor Commented:
Out of all the customers that have called us this morning, so far that registry edit has worked:

reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\system /v LocalAccountTokenFilterPolicy /t REG_DWORD /d 1 /f
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Networking

From novice to tech pro — start learning today.