This is still happening to me on occasion and I'm trying to nail down the exact cause. I use ProfitUI, which has been patched for DoV. The first time I logged in on each computer after GU59, I couldn't add to collections. If I loaded the default UI and then went back to ProfitUI, the issue was resolved permanently. It seems like something isn't being initialized properly and it drives me nuts that I can't figure out what.
The fact that some people had the problem with the default UI and that clearing cache files helped is at least something to work with.
-= Therendil =-