Unfortunately, you've given us no information about your computer and what type of hardware you have installed. It's tough to provide much help without such information. Desktop/laptop? Processor speed? Amount of RAM installed? Age of computer? Turned off your popup blocker if you're using your browser to play the game?
Tried checking the game's website for the answer? Installed any patches that the game requires?
A quick check of the online game site shows a variety of discussions between the characters, but I don't play the game using the installed version.
Hope this helps.
I've recently loaded assassins creed on my computer, when i play the game i have no dialogue between the characters. I have all the sound effects but no dialogue, i don't know if that's the way the game is meant to be , but if anyone has played the game i would like to hear from you to see if this is normal. Any advice on this matter would be greatly appreciated.