Didn't know it had to be a blank slide (I know, you said "blank slide", but I wanted to avoid the brief flicker in between slides that occurs if I add a blank one).
No idea why the hyperlinks would have been set to go everywhere but slide 1, though, because I set them the same way I always do and it usually works. But once you told me about it, I just completely deleted the hyperlinks and set them again.
And now your trick with the blank slide works like a charm. Thank you so much for helping me out!