See if you can find the internet settings on the Freeserve site for Dial-up. (Keep or download the Freeserver installer too), then remove the current dial-up, and try manually configuring the connection. If it doesn't work, then just run the Freeserve installed to get you back online.
It could be that at peak times the service isn't as good. I used to have the same problem with UKOnline. At busy times I would fail to connect or connect and get no pages loading.