In general, error 4 means that the injection failed.
Specifically (in case you have some WinAPI knowledge), it fails to call the GetProcAddress function, probably because the address is different in the tweaker's process and in the explorer's process.
I don't know why that happens. I know it can happen when enabling compatibility settings, but you've said that yours are disabled.
You say that the issue started after updating NVidia drivers. Could you try disabling, or temporarily removing them, and check whether they cause the issue?

Should be fixed in v4.5.4, please try it.

Please check the properties of 7+ Taskbar Tweaker. Does it run in a compatibility mode on your computer?

Please try v4.5.4.

Are you talking about the tray icon?
Also, please try v4.5.4, which fixes a couple of issues.

A duplicate of:
http://tweaker.userecho.com/topic/515777-taskbar-b...

Fixed in v4.5.4.

Please try 7+ Taskbar Tweaker v4.5.4.

I managed to reproduce the issue. I believe that it should be fixed in v4.5.3.1 beta. Please try it.

I cannot reproduce it. Screenshot below.
Please provide the following:

• Your OS version.
• A screenshot of your tweaker options.
• A screenshot of your taskbar properties.
• A screenshot where the bug can be seen.