Possible cure for this problem at TechNet. Look to Bottom of page, this fix sets up a delay so that the mapped drives aren't accessed until you click on them. I don't have this problem so I can't test it out on Win 7 but it's the only fix I found for the problem.
Help! Howto delay maping drive until network is up?
To faxedhead below, you just reposted the link that was on the bottom of the page which I already posted.
You can download the utility here . If you are the one who wrote this utility then hats off to you.