It's called lag and the same thing happens to your opponent in the first half. There are varying levels of lag, depending on both of your internet connections but it's part of the online game so you have to get used to it for a half.
In PES4, one person hosted a whole match so the other player had lag for the whole match (and people played 2 matches to even things out).
Also, some naughty people run programs on their pc to take up their bandwidth and add extra lag for their opponent. This often happens near the end of a match or in extra time when they are losing.