Here's a link to some information from the EU about the constitution:
Also, after the no-votes in France and the Netherlands, it seems that there is a variety of reasons why some people in different European countries are opposed to the treaty ... fear of a country to loose it's independence, reduction of benefits, sharing work with a foreign workforce, suspicion of neighbouring countries, admission of other countries to the EU, fear of exportation of Jobs to countries less bothered with controlled wages and so on. If all this would happen, is a different question, but some of these things are on peoples minds and maybe they don't see that there are not only disadvantages, but also advantages.
However, for hundreds of years there were all these individual countries in Europe and they have to give it time. To form such a complex thing as the EU, the treaty etc, takes time and can't be done in a day.