RAM doesn't have to do anything with CPU usage.
What's your processor's speed?
It looks like WLM doesn't have any optimization at all: It will still render any non-visible animated emoticons.
Many animated CEs will use lots of CPU and the only way to "fix" this is to close and reopen the conversation window.
You can also disable CEs but you probably don't want that.
I really wish Microsoft does something to fix this...
I'm speaking from experience btw (1.06 GHz processor on a laptop, where CEs make WLM's CPU usage go up )
/ 
