What's been said regarding face time, office hours and matching domestic expectations is true. Although foreigners are usually held to a different standard in Korea (which can have both drawbacks and benefits) sometimes the Korean boss decides to level the playing field. This can have disastrous consequences to a foreign employee who is used to the expectation that work time is productive time (well, until the age of the internet, that is) and if work is done then lets get the hell out of here and enjoy our free time.
(There was a great pocketbook that was put out in dual languages called "Ugly Koreans/Ugly Americans." If it's still published and you see it wonderboy416, pick up a copy--it's a great conversation piece back home, especially with Koreans, and was only $6 when I was there and has cute cartoons. It went into many of the potentially insulting cultural differences between Koreans and Americans (Westerners) and office time was among them. It was part of a series that went into Japanese and Chinese culture, though when I compared them some of the examples were copied word for word, indicating some cultural similarities. The book was very accurate when I was there)
The employees leave when the boss leaves, regardless of whether or not the work was done. Often this allowed for an easy company trip to the local bar or karaoke bar, at least in Korea. But woe to those who don't drink alcohol...
At a university job in Korea I was expected to have office hours and spent four weeks a year sitting in the office for six hours a day with no classes to teach. But if some minor university official poked his head in, or one of the profs needed something in English edited, or if a student wanted to talk about doing his masters in America then I was a convenient resource.
But at the private schools they usually let this rule slide, which is why I believe wonderboy416 is getting a little screwed over here. Not that there aren't far worse issues that can come up because I saw them, but unless things have really changed I don't think its standard. Whether its worth fighting over is really up to wonderboy416.