Yes, adjust your clutch per the service book. Also, it may be that your tranny pulley is on too tight.
I'd say unloosen it, and retighten to the proper torque according to the service book.
It does have red locktight on it and come like that from the factory, even when you buy a new one it's got some on it. You may want to apply a little more, or just buy a new one.
Also, another tip, tighten it to where the locking screws match, if you go too far, unloosen it completely, and try again, don't unloosen it to get it to match up.
Another thing, it may also be that they didn't tighten and align the rear wheel correctly, and it bound itself up again. It's really not hard to check the alignment and the belt tension. Heck, there is even a rough gauge right on the belt cover itself. Again, it's all covered in the service book. I go and check mine every oil change along with everything else that might seem to get loose or worn during use.
I can say, you don't want it extremely tight, because it will go out on you and you'll be left stranded and it puts a lot of stress on the output shaft on the tranny. Belts are not as forgiving as chains too. But even chains, you don't want them to be super tight either.