Kvitova, a one-time world number two now down to eighth in the rankings, is attempting to reach a second Wimbledon final.
Her cause was helped following Maria Sharapova's second-round defeat, but the 23-year-old Czech now finds herself in danger of tumbling out of the tournament.
The 2011 Wimbledon winner took the first set 6-3 against Russia's Ekaterina Makarova in their third-round tussle on Court One, but the 25th seed won the second 6-2 and was a break up at 2-1 in the decider when bad light stopped play tonight just before 9pm.
World number seven Angelique Kerber tumbled to defeat from the jaws of victory earlier in the day.
Kerber looked on course to make easy progress to the third round when she took the first set on Court Two and led 5-1 in a second-set tie-break, but her opponent, world number 46 Kaia Kanepi, hit back to defeat last year's semi-finalist 3-6 7-6 (8/6) 6-3.
To make matters worse for Kerber, she was subjected to vile abuse on social media after she saw the match drift away.
Sharapova's conqueror Michelle Larcher de Brito bowed out to Italian Karin Knapp, the Portuguese player losing 7-5 6-2.
Sloane Stephens and Petra Cetkovska took a set apiece before they came off due to the fading light, while Puerto Rico's Monica Puig was a set and a break down against Eva Birnerova.
France's Alize Cornet, seeded 29th, bowed out after losing 0-6 7-6 (7/4) 6-2 to Flavia Pennetta on Court 12.
Pennetta, who had a walkover against second seed Victoria Azarenka in the second round, was relieved to make it through after surrendering the first set so easily.
"I don't know why I played like I did in the first set," the Italian said.
"After the first set I just tried to hit more and more, with a little bit of power and my serve starting to work a little bit also."
Pennetta will next play Belgium's Kirsten Flipkens, who beat Serbian Vesna Dolonc 6-4 6-2 in the third round.
British prospect Laura Robson moved through to the third round for the first time after she beat Mariana Duque-Marino in straight sets on Centre Court, by a 6-4 6-1 margin.
The Londoner's Canadian friend Eugenie Bouchard crashed out of the tournament though, losing 7-5 6-2 to Spanish 19th seed Carla Suarez Navarro.
Poland's Urszula Radwanska failed to join her fourth-seeded sister Agnieszka in the last 32 after losing 4-6 6-3 6-4 to American Alison Riske.