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May 1 marks five years since the European Union opened up to bring former eastern bloc countries into its fold, taking it to 27 members. But instead of fanfare and fireworks, the mood is muted in New Europe and among the E.U.'s veterans.

The post-1989 boom in central and eastern Europe — when new E.U. members enjoyed average GDP growth around 5.6% per year from 2000 to 2008 — has been punctured by the current economic downturn. Many of the new E.U. countries are on a downward spiral as credit dries up, demand collapses, currencies tumble and unemployment surges. Some of the E.U.'s older members are suggesting they may have opened the doors to the club prematurely: they grumble that the new members are dragging the E.U. down further into recession. And there are calls to...