I think that this is a genuine issue that many former Communist governments will have to deal with. The old Soviet bloc countries and client states are at a point in time when many people are looking back at Communism with nostalgia. They forget the crippling shortages, government corruption, and police state brutality.
Yes, I think that communism will spread back through eastern Europe to replace current socialist parties, because people are looking for what went wrong with the current financial crisis. Governments tend to go in cycles, from democracy to socialist and then to communism. It is only a matter of when it happens.
People have a short memory, for sure, but people don't have such a short term memory that they can quickly forget the horrors of communism in the world. China is the sole example of a successful communist state, but communism there led to the deaths of 25-30 million, and they only advanced after allowing free market enterprises.
No, I do not think that the communist party will spread back through Europe, because the United States will not let it. The United States has spend a lot of time and money and troops to stop the spread of communism in different parts of the world, such as Vietnam.
Given the world's recent models for Communism I doubt it will spread back through eastern Europe to replace current Socialist parties. The more we learn about this different social systems the more we learn and I believe from experience we are finding that no one system really works on its own.