Somehwo I always manage to screw stuff up. The other day I connected my iPhone to my Mac and it fired up -as it should- iTunes. However, iTunes told me that I should "activate my iPhone or that the SIM was damaged". I have a jailbroken iPhone and a fine SIM card, rebooting the iPhone "solved" the problem. However, it triggered something else that I only found out days later; the Youtube application still was not activated and tol me when I started it

You must first connect to iTunes with an Internet connection to enable Youtube

And then the application stopped. It seems that this is "normal" behaviour when you unlock your phone with ziPhone. However, I jailbroke my iPhone with iNdependence and it has been working fine for month.

The solution for ZiPhone users worked for me as well however. Some say that installing a "YouTube fix" program via the installer application will work, it did not for me. But all you have to do is copy three files to your iPhone, even if you do not know anything about UNIX an easy task.

Just download these threefiles. Start a SFTP client on your machine, copy the files in /var/root/Library/Lockdown to your desktop for backup reasons and copy the three files you downloaded to the same location. The userid to do this with is "root", the password "alpine".

Worked for me, I can use the Youtube application again, thanks to macriot!