I am still having problems with this too. I have multiple saves from the Ice Plains and still nothing. I went back and tried to make manual saves at the beginning of the level and at the end and Witcher 2 still doesn't recognize the save. The GOG forum is still trying to figure this out too.
No. It would only connect through steam as a copy protection measure which CD Projekt doesn't jive with. The Witcher 2 is using a date check version of Securom Release Control with unlimited licences but only 5 computers being able to run the same copy at a time. The version sold through GOG has no DRM.