DNS propagation can be a real pain if you are an impatient person. The reason it takes a while for any DNS changes to take affect is because your ISP caches their DNS records to improve speed with DNS queries. This means that you have to wait for them to update their cache before your DNS changes will be reflected.
A simple recommendation is to use Google DNS. It is free and public and works with all ISPs. We've noticed an increased propation time by using Google DNS, changes seem to be almost instant.
You should also flush your DNS. Please read this KB Article about flusing DNS.
Give it a try and see if it works for you!