Are the nuveau riche of Eastern Europe the ex-communists living off other people's money?

Maybe and maybe not. If the people that are "NEW MONEY" are there because they were creative and earned the money I dont see how they are "LIVING" off of other peoples' money.

They earn a living unless they are stealing it from others.

Why would they do that... they're rich.

I believe, though am no expert, that the super-rich are generally the recipients of state monopolies that have newly been privatised. These have often been sold at reduced prices to friends of officials. This is by no means a rule and I'm sure many made it fair and square. I think the new middle class are just hard working, talented individuals. I don't think communism ever really generated enough money to create that much wealth.

Of course.
They took $3000 from me at the Prague airport in 1988 and gave me 4 crowns on a dollar. To get into best restaurants and get a hotel, to see a special doctor, get certain products in store, etc., often, bribes were involved.
Over the years, they have accumulated a lot of money and when communism crashed, they were no longer hiding it and began to enjoy capitalism.