I'm also having the problem/bug with the Enter key. Every game that I tried, that requires that key at some point, is absolutely unplayable, since the whole NG player freezes at the moment I press it, forcing me to close it via right-click, because even the window itself won't respond anymore. Usually the game's music keeps playing, dunno if that's helpful in any way.
I also encountered a few games that didn't load and just offered a white screen, which were most of the escape games by @selfdeviant. Since I last tried playing them, I came across the Doom triple pack, which required me to download flashplayer 10 (although I already had a more recent version downloaded). So I did it, in hopes it would work, and it did, I was able to play Doom. The other 2 games there require the use of the Enter key again, so I still can't play those. But now with that flashplayer 10 downloaded, the escape games by selfdeviant work again, like they used to in the old flash times.
So in other words, downgrading my flashplayer disposed of the white screen bug (at least for the escape games, don't know about other games that I encountered so far with that problem).
It's no real solution, but to those who also get the white screen, try playing the Doom triple pack, download whatever version of flash it links you to, and try again, maybe it works.
Now I'm still concerned about the enter key bug, because it is very annoying since I want to get into the sites highscore list, which will be much harder if missing out on like 1/3 of all games.
I have windows 7, 64 bit, 2 GB CPU. Hopefully some expert will find a connection between the flash version, the PC specs and the NG player and come up with a solution for everyone.
(By the way, this is my first forum post ever, so if I did anything wrong - please be kind. Thanks in advance c: )