Couldn't you just add more frames of the same thing? i.e. If you have someone talking and you have two frames of their mouth closed and two of their mouth open, add a frame of the closed mouth and a frame of the open mouth to each to make it look slower.
I tried that, but Imageready decided to be a smartass and add the duplicated frames to the end of the .gif after I saved it.
You could use these programs. http://www.ulead.com/ga/features.htm (free trial) or http://www.gimp.org/
^ This, also, if you could PM me the image hosted somewhere I could attempt slowing it down for you. No promises though because I haven't done anything like this in a while...x__x
I'm not sure about that because to slow it down I'd be adding frames, but speeding up would mean taking them away which would just make it look choppy x__x.
Do this, and move the frames to where you want them on the timeline. I'm not too sure though, it's been a while since I used Imageready.