Sometimes when loading the list of books, dslibris will freeze. Oddly though, it still goes into standby when I close the screen, and wakes up when I open it. Unfortunately, there doesn't seem to be much pattern to the freezing. I've had it work fine for weeks, then start freezing every few times I run it, then work fine again for a month. The books are all epub files, mostly around 200 KB.
I have a DS Lite with a DSTT cart and memory expansion GBA cart (Nintendo). This issue has shown up on both the stock firmware and FlashMe.