Sebastien Loeb, Thierry Neuville and Jari-Matti Latvala had already all run into trouble on Friday morning, and Solberg joined the casualty list on the afternoon's second stage.
The Norwegian, who was running 23s behind leader Hirvonen's Citroen, went off and damaged his Ford's right front corner on the Tergu-Osilo stage.
That left Hirvonen a minute clear of the field.
Evgeny Novikov is now his main rival, the Russian having risen to second thanks to the usual frontrunners' dramas and his own speed - including two stage wins.
Novikov is 1m08s clear of his M-Sport team-mate Ott Tanak, as the young duo complete a great day for the satellite Ford squad in their provisional podium positions.
Both moved up as Mads Ostberg fell back. His Adapta Ford developed differential problems in the afternoon and was front-wheel-drive only for a while. The loss of time dropped Ostberg to seventh.
All of that has helped Sebastien Ogier and Andreas Mikkelsen into astonishing fourth and sixth places overall in their Volkswagen-run Super 2000 Skodas. Chris Atkinson splits them.
- Sebastien Loeb
- Thierry Neuville