TFS lets me do compare and checkout, but not checkin

Question

I have been using TFS in my visual studio 2013 for some time now but now I have a problem.
When it was initially setup I logged into TFS from VS using the domain\Administrator.
But company policy has changed and now the password is changed and I dont know it anymore.
But my own domain user has been granted administrator rights so I think ok no problem next time I start VS and TFS asks me to login I provide my own account.
This did not work I got tons of errors so I had to go to Control Panel and remove this credential from credential manager.

So I started VS again and let someone type in the pass for Administrator again, and click on remember.

That seemed to work, I can do a compare of files and it is correct.
I am also able to checkout files for editing.
But when I want to check in than it displays an error for a split second and it shuts down my project in VS.

After numerous tries I was able to capture a screenshot of the error (it only displayed for a split second).
This is the error :

I have no clue what this thing is talking about and I am hoping someone here can push me into the right way to find a solution for this.

Where can I find this workspace and how can I give it permissions ?

I am using visual studio 13 on local computer, logged in to domain and my user account has administrator rights.

EDIT:

I found a screen in VS to edit the workspace. The permissions are currently on Private Workspace.
So set it to public and now I also cannot do Compare and Checkout anymore.
Setting it back to private does not helps I keep getting this error now.

Any suggestions ?

Edit:

There seem to be 2 workspaces with the same name but I can only see on in manage workspaces. Maybe if I can get rid of one somehow.
In this screen I can see 2 workspaces :

How can I get rid of the second ?

EDIT:
IT seems that VS keeps searching for the wrong workspace.
See this screenshot :
I configured a new workspace PC_GUIDO_2 but if I do a compare it keeps searching for workspace PC_GUIDO even if the workspace combobox says PC_GUIDO_2.
How can I force it to stop searching for that workspace ?

Answer 1

Please try following below steps to fix the issue:

1. Make sure your account has the check in permission for the project. (Administer Server > Version Control > Set the permissions)
2. Close VS
3. Delete the VS client caches
4. Start VS as administrator (Right click and run as administrator) and DO NOT LOGIN WITH VISUAL STUDIO
5. In team explorer connect TFS with your account
6. Manage Workspace to delete current workspace "PC_GUIDO"
7. Create a new workspace and map sources to new local folder

Then check the issue again.