I'm having trouble saving games and achievements as well, and it's annoying as hell. I think it only happens when the browser is closed abnormally, for example if I shut the computer down while the window is open or if the computer closes by itself for whatever other reason. I rarely close my browser, so I've started over about 5 times already.
 "Cards Wars"){kind=icon}
 "Bloons TD 5"){kind=icon}
And what is your OS/browser?