Cannot open folder and NO error message

[ErikJan]

(as my previous problem got resolved -by myself- after I posted here, let me try with my second problem ;-))

In C:\Windows there are folders I can open, folders where I get a UAC when I try to open and folders where I have no access and get an error message if I try to open. All normal.
There are also folders however where NOTHING happens if I double click (or right-click en choose Open). The folder does not open and there's no UAC nor any error message.
If I look at security, it tells me I don't have read permissions (but remember: there was NO error message before). If I go to Advanced, Check Permissions and confirm the UAC prompt, I see SYSTEM and Administrators groups with Full Control. I can confirm, I'm in the Administrators group.
If I type my UserName in the "Effective Access" tab and have the system check my access, I indeed get confirmed I have Full Control (all attributes are shown with a green check-mark)
If I try to Rename the folder, after a UAC prompt (logical), I can (!).

If I open a CMD prompt I get access denied, in an Elevated CMD window I DO have access to the folder.

I'm confused... thoughts? Suggestions?

[StuartR]

Are these system folders or user folders?
Can you log in to the real Administrator account and access them?

[ErikJan]

Some are system folders (but they can be access normally on similar systems). No, I can't log in to the real Admin account (but an elevated CMD prompt does give me access)

[StuartR]

How strange. Can you run explorer.exe from an elevated command prompt and see what that does?

[ErikJan]

Gets more weird now... I launched Explorer from an elevated CMD prompt. Opened the folder and got a UAC. After that I had access.
Now I opened a normal Explorer and tried it there: I now have normal access. All other previously blocked folders now trigger a UAC.
Guess that solves my problem (understanding what happens is another thing but I'm happy).
Thanks Stuart!

[StuartR]

Weird! I guess all's well that ends well