Yep, it's one of the many things that needs to be re-enabled after a restore. Don't forget your ringtones and your default ringtone as well. I had to reset all of my GB ringtones...
Its surprising how many "tips" and instructions you can find in the online iphone manual
I downloaded it just for a quick browse but it has just about everything in there. With Apple products generally not coming with a paper manual I normally forget to look online and just work my way through it, but its definitely worth downloading.