This could be one of several things. Neither browser can get online if the network isn't ready but also the other startup programmes might be interfering. Press your Windows key and R together then into the Open box, type msconfig and press Enter. Click eth StartUp tab and scroll through the list, unticking anything that doesn't really need to start when Vista does. They'll all still work when you want them but things like Adobe anything, MS Office, photo software and the like can wait until they're called for instead of slowing the system down at boottime.
So long as you don't untick your firewall or anti-virus programme, no harm will come of this and you can reverse the changes later if you wish. When you finish, click Apply and OK, restart as suggested and when the system comes back up, tick "Don't show this message again" and hit Enter. On the next restart, things should be quicker.
What is your system memory and hard disk free space?