I understand your frustration. Adobe DRM is aimed at a non-technical audience: but it is a very technical solution requiring too much careful consideration of detail in use even when it works well, and a nightmare when it doesn't. I especially admire the librarians who have to help their customers through this quagmire. There's at least one other ongoing thread with issues on the Glo as well.
I think this sounds more of a Kobo issue than an ADE one. The only other suggestions I can make: a factory reset of the Kobo, and start again. I assume you have all the books safe and sound on the PC (or Mac)? If not, copy them all back before the reset.