Lance Armstrong moved into a 55 second overall lead after CSC rider David Zabriskie fell approaching the finish on the stage four team time trial.
Yellow jersey wearer Zabriskie and his CSC team looked on target to take the stage win but the American took a tumble just over 1km from the finish.
CSC finished two seconds behind Armstrong's Discovery Channel team and Zabriskie is now over a minute behind.
Armstrong's team-mate George Hincapie is second in the overall standings.
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1608: American yellow jersey-wearer David Zabriskie takes a tumble approximately 1km from the end leaving his CSC team to race ahead - and they finish two seconds behind Lance Armstrong's Discovery Channel team in 1hr 10mins 42secs. Armstrong takes the yellow jersey while Zabriskie, having fallen over 1km from the end, falls to ninth, one minute and 26 seconds behind. Armstrong has a 55 second lead over second-placed George Hincapie, also of Discovery.
1605: Lance Armstrong leads Discovery home in 1hr 10mins 40secs, 34 seconds ahead of Jan Ullrich's T-Mobile team in second.
1600: Phonak finish in third so far in 1hr 12mins 10secs, 56 seconds behind leaders T-Mobile.
1557: Gerolsteiner finish in fourth so far, one minute and 30 seconds behind leaders T-Mobile.
1550: Jan Ullrich and T-Mobile take the lead with a time of 1hr 11mins 14secs, 18 seconds ahead of Liberty Seguros in second.
1546: CSC go through the 46km mark in 47mins 08secs, six seconds faster than Discovery Channel. CSC are travelling at an average speed of 58.1kph.
1542: Discovery Channel go through 46km in 47mins 14secs, one second ahead of T-Mobile in second and 43 seconds ahead of Phonak in fourth.
1541: Liberty Seguros power home in 1hr 11mins 32 seconds to take the lead. They have taken 48 seconds out of Credit Agricole in second.
1536: Credit Agricole take the lead with a time of 1hr 12mins 20secs, 24 seconds ahead of Illes Balears.
1531: Illes Balears finish in 1hr 12mins 44secs, 21 seconds ahead of Liquigas in second.
1527: CSC go through the 25km mark in first, six seconds ahead of Liberty in second. Discovery and T-Mobile were joint third, 15 seconds behind.
1526: Rabobank finish in third in 1hr 13mins 27secs, while Jan Ullrich and T-Mobile go through 46km in first place in 47mins 15secs - 13 seconds ahead of Liberty.
1524: Phonak were 33 seconds behind leaders Liberty at 25km but appear to be stepping it up. Lance Armstrong's Discovery Channel team are clocked at 70kph.
1523: Quick Step finish in fourth in 1hr 13mins 44secs.
1521: At 46km, Liberty are in the lead in 47mins 28secs, 37 seconds ahead of Credit Agricole in second.
1519: Jan Ullrich's T-Mobile are second fastest behind Liberty at the 25km stage - nine seconds behind. Lance Armstrong's Discovery Channel team are equal second.
1516: Francaise des Jeux finish in seventh so far, two minutes and 20 seconds behind leaders Liquigas.
1515: There is a lot of debate on our messageboards about the rules, which mean no team will lose more than three minutes however badly they do.
Bioniclee says: "I think the new rules are totally unfair - why should the better team be penalised for being better than the rest?"
But Chilean_Llama reckons: "The new rules help some way towards not having the race won or lost too early."
1508: Bouygues Telecom finish in 1hr 13mins 47secs, third so far and 42 seconds behind leaders Liquigas.
1503: Liquigas take the lead, clocking 1hr 13mins 5secs, six seconds ahead of Davitamon in second.
1500: CSC are off the ramp last. America's David Zabriskie is the current owner of the yellow jersey.
1457: Cofidis finish in ragged fashion and some of their riders are almost caught by Davitamon who take the lead in 1hr 13mins 11secs. They have a one minute 27 second lead over second-placed Euskaltel.
1455: Defending champion Lance Armstrong rolls into action with his Discovery Channel team. The time trial is expected to be a straight race between Discovery and CSC.
1451: Saunier finish in 1hr 15mins 45secs and are currently third, one minute and seven seconds behind Euskaltel
1450: Phonak are off the ramp and expected to do well. America's Floyd Landis is 6th in the general classification.
1446: In come AG2R in 1h 16mins 02secs, one minute and 24 seconds behind current leaders Euskaltel.
1445: German team Gerolsteiner are off the ramp, with Levi Leipheimer, ninth overall last year, their main man.
1441: Liquigas are fastest so far at 46km in 48mins 20secs, 21 seconds ahead of Davitamon. Saunier and AG2R are over two minutes behind.
1440: T-Mobile, with Jan Ullrich, get under way. The team are not the force they have been in time trialling.
1437: Davitamon go through the 46km mark in 48mins 41secs, 45 seconds faster than Euskaltel. Lampre finish the race in 1h 14min 48secs, 10 seconds behind Euskaltel.
1435: Italian team Fassa Bortolo, with Fabian Cancellara, are away.
1433: Euskaltel finish in 1h 14mins 38.48secs.
1430: Dark horses Liberty, with some useful time triallists on board, set off. Joseba Beloki and Robert Heras are their top riders.
1426: Lampre are 32 seconds behind Euskaltel at 46km and Saunier are 1min 16secs adrift. AG2R are five seconds further back.
1425: Credit Agricole get going, including third-placed Laszlo Bodrogi of Hungary.
1420: Spanish team Baleares are away, young hope Alejandro Valverde in the bunch.
1415: Rabobank, including Marc Wauters, 21st overall, Erik Dekker and Michael Boogerd, get under way.
1410: Euskaltel reach the 46km mark in 49mins 26 secs.
1409: Quick-Step, including green jersey wearer Tom Boonen, hit the road. Francais des Jeux look in some disarray, Bradley McGee gesticulating wildly to his team leaders.
1405: Giro d'Italia specialists Domina Vacanze get under way. Ukrainian Andriy Grivko is their leading rider in 39th.
1400: Off go Franšaise des Jeux, 21st last year. Australia's Bradley McGee almost runs into the bike in front as the team crank up. Baden Cooke and Sandy Casar are also among their number.
1355: Bouygues Telecom get under way, with Frenchman Walter Beneteau their leading rider in 25th overall. The French team also have Thomas Voeckler and Laurent Brochard in their ranks.
1350: Liquigas, including Italy's Stefano Garzelli, are seventh out on the road.
1326: Michael-Stephen Dempsey emails us to say:
"With the strategic way the past two stages had to be ridden I expect Discovery Channel to try and make a statement today."