According to an article on Wiitalia, Nintendo of Europe enlisted a postphone note on Mario Party 8 in the UK:

Nintendo rammarica in informing the customers who because of a problem of production with the English version of Mario Party 8 the launch date has been postponed to the 13 July 2007. We are working in order to resolve the problem and to assure that this amusing party game for families can be appreciated to more soon possible.

Mario Party 8 was already released back in May for North America while other locations won’t recieve the game till July or possibly later. Production predicaments have been a concern lately, especially with games such as Super Paper Mario and Trauma Center in the UK area. Hopefully NOE will sort the problem out soon. The qoute above was the result of a translation.