If no one here can help call a wallpaper store. My husband and I did some wallpaper in our last home and I wiped down all the seams with a clean wet rag while they were still wet and didn't have that problem.

I've used DIF to remove wallpaper -- it dissolves the old glue quite easily. You might want to try a little of that and apply very carefully: you don't want it to seep into the seam and loosen your wallpaper. Would be prudent to dab some on a piece of wallpaper scrap you might have, just to make sure the DIF doesn't damage the paper either.

It might not be all glue, it could be the seams of the paper itself. Most wallpaper is printed on top of a white back and if your seams are not super tight, the white edge of the paper shows. Professional paper hangers often overlap the edges of the paper slightly and do what is called a double cut through both layers of paper so that the seams are really tight.

If that is the problem, there are some tricks you could try. One is to get a small amount (a quart is usually the smallest) of acrylic paint matched to the main color of your paper and rub that lightly into the seam to help stain the white edge. I have used eyeliner on black paper, worked well.

If it is just glue, you could try a solution of TSP and hot water. As well as DIF there is a product called GooGone that might work for you as well. As javiwa said, test on a scrap of paper first to make sure it does not damage or remove the color in your paper as well, and work gently.