Vista - About for WLM can't remember my login information

I update my yahoo messenger's latest version (this msg from it's update
program)
and their has also to install Yahoo Toolbar in my computer.
When I have finished to install this update I try to perform my WLM to login
and
my WLM can't remember my login information(account name & password) at all.
Even I'm going to restart my computer and there have the same situation.
I make sure I always to set WLM to remember my login information.
In google I get this problem cause by Yahoo Toolbar for sure and I want to
know how to fix it and except using windows system restore .

I can't to describe for clearly please to forgive me
THANKS FOR YOUR REPLY