Hope you didn't feel like beating the game anytime soon.
A glitch in the Wii version of Tomb Raider: Underworld has sprouted up, making it impossible for some players to complete the game without jimmy rigging it or re-playing potentially large portions of the adventure.
In the Coastal Thailand area of the game, Lara must take a crazy leap from a rock outcropping to latch onto a pole and use her bodyweight to pull it down - opening the passageway to the next area in the process. Apparently, the crucial lever is sometimes absent in the Wii version of the game, causing Lara to splash down into mucky waters without the ability to proceed.
Rather than offering to replace affected games, Eidos Interactive has taken a slapdash approach to solving the problem. It suggests players either a) re-load from a previous save point or b) use an SD card to download a set of saves the company is providing to bypass the glitch. The latter wipes out any treasures you've collected along the way. Neither solution is particularly preferable.
UPDATE - In an official statement issued today on the matter, Eidos said the problem is an "extremely infrequent" bug that will occur on rare occasion.
"Eidos sincerely apologizes to anyone who has experienced this frustrating problem," the publisher said in a press statement. "The quality of our games is paramount to us, and the Nintendo Wii version of Tomb Raider: Underworld went through three separate QA testing departments prior to release. Regrettably, anomalies such as this do occur occasionally in videogames, despite the best efforts by publishers to avoid them."
Eidos is encouraging anyone who encounters the problem to visit this website.