Which browser are you using? It sounds like something is funny is happening with the random number generator and it's outputting the same numbers every time. If you close the browser down and re-open it does it keep happening?
It sounds like there's something weird to do with the way your browser is initialising the seeded random number generator, but I don't know what could be happening or what I could do about it. Playing it in a different browser or clearing your browser's cookies might fix the issue, although you'd also lose your saved game and any high scores. Sorry I can't be of more help.