From: United States
I was having problems with Sodoku last night - finally gave up as the game wasn't enjoyable anymore. I tired again, same problems. I read the entering pencil mark post, did what you recommend and clear cash and reopen browser. Nope. It's still buggy.
The biggest problem is when you start entering pencil marks, once you actually fill in the square (ie I think this square is "1"), it does not grey out the rest of the potential spots anymore. If you go and manually delete the pencil mark, then the square turns back to grey, but not until then.
I also don't like the new interface - you have to be VERY precise in where you click to enter the pencil marks - otherwise it fills in the actual number.