Shipping is threatened by a late start and because many ships are based in countries which have not been working on y2k. Modern cities are made possible by water treatment plants and sewage treatment plants. These plants use embedded systems and require electricity and telecommunications. If utility systems fail, high rise buildings could become uninhabitable. If heating systems fail for several days in the winter, pipes may freeze.
People then lose water.
When the pipes thaw, the buildings sustain water damage. If there is widespread damage, months or years may be required to repair the housing stock. Furthermore, if people lose water, they may drink from rivers and lakes. There could then be a health care emergency which might last for months, even if utilities were restored in a few days. If governments are unable to function, decentralization may occur, with the possible rise of local mafias, rather like what has happened in recent years in Russia.