Can't align object to guide

Hi Indesign Gurus. I’m hoping someone can help me figure out this problem. I’ve searched InDesign Secrets and Googled the issue extensively, but I can’t find any solutions. I’m going INSANE! Here’s my problem: I’ve got a box. I’ve got a guide. I want to align the box to the guide, but when I drag the box it will only allow me to move it in one pixel increments. The guide is not on one of those increments so the box just snaps above or below the guide, but not ON the guide. It’s maddening. I’m working in an 80 +/- page document and up until today I’ve never experienced this behavior. Any advice is much appreciated.