We don't know why, either.
Planned for release tomorrow in North America and Europe for Xbox 360 and PC, the Return to Ostagar downloadable content is now being put on hold with no explanation given.
"We're sorry but the planned Return to Ostagar downloadable content scheduled to launch on January 5th has been delayed for all platforms," said Community Manager Chris Priestly on the official forums. "We will update you as new information becomes available."
The PlayStation 3 version was planned for release "later" in the month, BioWare announced last week. Given that the content has been delayed on "all platforms," this may mean Return to Ostagar won't see a release until late January at the earliest.
We've contacted BioWare for any additional info and will update this post as soon as we hear back.
MovieMiguel.com