Just a guess....try going over the magic pink areas again.....make sure the color is 255, 0,0.  Sometimes, if you don't have those areas colored exactly right, they will not look right.  Also check your left sizing margin, to make sure it is inside the actual image.  Hope this helps.

The other element is a "button". It's a mask for the rounded edge of the titlebar. To fix it, go to the tiltlebar buttons section (in the UIS2 frames section) and select the first button on the list (violaceous\b-bar.bmp) Go to the position tab and move the button to the left. To me -5 looks to be the correct position.

If I have been unclear, I'll post a screenshot for you.

Thanks, forgot to tell that together with the fix for the margin I also corrected this.

I've adjusted some other things too, and now I'm very happy with my new old skin (although of course still some things are missing like start menu, taskbar, Internet Explorer 8 design etc.).

I'm impressed, it's really a cool thing this SkinStudio, unbelievable all the things you can modify! But it's a time killer, I spent the whole day with it - but at least it was worth it for this nice skin

Yeah, that was my though as well.

Only the concept with a plan for all objects required and how they shall look like including the different states for buttons, checkboxes and so on. Maybe different styles. Afterwards the work with Photoshop. Testing. Different versions of programs (e.g. Internet Explorer), unforseen behaviour of WB or SKS.... 

Respect!

So it's a very intense hobby if one wants to create really good skins. But it's a very nice job, better than model railways (if this is called like this in English) or such stuff 

P.S. OT: sorry, I don't find a setting for notifications of answers/updates in a thread, can somebody tell me where this is located?

No settings for notifications (like email notification) but you have seen this, I'm sure: