Suddenly can't select cyan guide lines

Suddenly, out of nowhere, I can no longer select and/or move the cyan guide lines on any Illustrator document. I was able to earlier today, and just BOOM. It stopped working. I've restarted the program and my computer but the problem persists. Please don't tell me Adobe has disabled this feature... I hate that it doesn't work in Photoshop, but I absolutely must have it in Illustrator. I've always been able to click on the ruler to create a cyan line, then drag it and use my arrow keys to move it to create a guide for placement inside a box. I'm using version 29.0, and like I said, just today it was working fine, but out of nowhere it stopped and restarting does nothing. And I haven't changed any settings. Please help!