you had to add another profile I am assuming ff crashed or something, so its lock file wasnt properly removed
close firefox then if you look in your Documents & Settings\<username>\Application Data\Mozilla\Firefox\
there should be one or more folders in there, one called default.xyz (xyz being three characters or numbers) go into this one and delete the parent.lock file if it exists, same for any other folders
the default.xyz one is the one that is created when you install Firefox, so it should always be there, afaik any other folders represent other profiles you have created.
also in the default.xyz is a file called bookmarks.html this contains all of your current bookmarks if you want to copy that about