The Episodes for GTAIV have been delayed a couple weeks on both the PS3 and PC. Rockstar Games made this statement as to why:

Due to a last minute game submission request from Sony Computer Entertainment Europe to edit some of the in-game Liberty City radio station, television, and internet content – we are forced to delay the worldwide release of Grand Theft Auto: Episodes from Liberty City for both PlayStation 3 and PC for an extra two weeks.

They will now be released on April 13th in the US and on the 16th in Europe. The PS3 leaderboards in the Social Club will also be down for maintenance from March 22nd and will extend for a week, to prepare for the launch of the Episodes. Why two weeks?

Those game changes sound pretty minor. Why does the game have to be delayed a whole two weeks?
Unfortunately, with each round of changes comes fully re-testing the game and a full re-submission to PlayStation. This is the nature of the game submission process. Believe us, if we could expedite the turnaround any sooner – we would. We are dying to get this game in the hands of fans who’ve waited for it for so long in the first place.

Via Rockstar