It may be the 64 bit kernel at work. I can play FB games just fine with the 32
bit. The 64 bit kernel can be a little buggie with Linux. However, there is
plenty of V and malware on FB and the game maybe seeking a door to put a coin
under the pillow. With windows there is plenty of doors leading in the hall
way to the kernel. With Linux. The doors lead to this door and go this this
door. It is not easy to get to the key maker of the kernel. So you may want to
install the 32 bit kernel.

It is strange though that this game used to work. If I install the 32
bit kernel, then it will not be able to access the 8 gb of ram that I have?

Possibly an issue with Linux Flash 64bit - this is still a "work in
progress" and every once in a while an update from Adobe comes through
the normal update channels.

Try installing a different browser such as Chrome or Opera as the
flash plugin for these may work better. Firefox is the default browser
in Ubuntu and I've found it's not as good as it should be !!