It may be a USB driver problem in your computer.One of those Windows glitches.
Do you know how to use Device Manager? (No idea what it is in German, sorry.)
In my XP it’s Settings/Control Panel/System/Hardware (tab)/ Device Manager.
Scroll down to USB controllers and you should see that yellow triangle and exclamation point. Right-click on that and Uninstall it. (Not Disable, uninstall).
Now reboot your computer and force MSC again and connect. Try a back USB port if you’re using a laptop–it gives more power.
(You shouldn’t be using a USB hub–it needs a direct computer connection.)
Your computer should find the generic USB driver that MSC uses and reinstall it correctly.
If that doesn’t work, the cord itself may be bad, but it is promising that you are showing Connected.