I'm talking about this issue that has been brought up in a thread on www.gamefaqs.com: http://www.google.de/url?sa=t&source=web&cd=1&ved=0CBcQFjAA&url=http%3A%2F%2Fwww.gamefaqs.com%2Fboards%2F959557-%2F57150001&ei=JiPpTKHpHYPwsgbNmKGPCQ&usg=AFQjCNGMqMfXvvDWR2TVn_yOd-I4ABkAUA
I've only recently started encountering it, which leads me to believe that it is indeed tied to a game patch. I haven't found any fixes so far, so I felt like it would be good to mention the problem here on the official Bethesda forums to make them aware of the bug and perhaps also have other people post in which situations they ran into this.
So far the only thing worth mentioning that I can contribute is that it has only happened when targeting animals or insects for me; I have yet to encounter a humanoid enemy who completely absorbed my explosive devices' damage.