Are you sure its for the 3Gs and not for the iPhone 4?
I'm not 100% sure, but I have downloaded plenty of sliders and stuff for my iPhone 4, but they wouldn't work because they were made for the 3Gs. Then I downloaded them to my sisters 3Gs and it worked perfectly, so it is a possibility.
What exact carrier logo did you install? I will install it on my iPhone 4 and see if it works.
I replied to another thread of yours on another graphic. My winterboard tutorials will have most everything you need. Start reading, start learning.