According to Reuters, the affected models are the PCV-RZ50, RZ60 and RZ70P. The problem is that the power supply in those machines can damage some power circuitry and lead to the PCs not switching on.
20,000 machines in Japan are affected, though a similar problem struck in the US and Canada last year with the same number of systems recalled there too. So far Europe has managed to escape the problem. ยต