So I looked into the log file and found:
[13-02-2015 18:53:25:409][..\..\..\EyesOfAChild\Code\EoC\App.cpp 1290 App::LoadLanguage]: Missing language.lsx file in 'c:/Program Files (x86)/GOG Games/Data/Localization/language.lsx'
[13-02-2015 18:53:25:565][..\..\..\..\..\..\LSFramework\Code\CoreLib\PackedFile_TOC.cpp 109 ls::PackedFileTOC::LoadTOC]: Number of files in TOC larger than buffersize! Files: 3439329280, BufferSize: 57404
[13-02-2015 18:53:25:565][..\..\..\..\..\..\LSFramework\Code\CoreLib\PackedFile.cpp 347 ls::PackedFile::Load]: Failed to load the pack file, Table Of Content is corrupt!
[13-02-2015 18:53:25:565][..\..\..\..\..\..\LSFramework\Code\CoreLib\PackedFileManager.cpp 214 ls::PackedFileManager::LoadPackFile]: Failed to load pak file: 'C:/Program Files (x86)/GOG Games/Divinity - Original Sin/Data/Engine.pak'!
[13-02-2015 18:53:25:612][..\..\..\..\..\..\LSFramework\Code\CoreLib\PackedFile_TOC.cpp 109 ls::PackedFileTOC::LoadTOC]: Number of files in TOC larger than buffersize! Files: 1023410176, BufferSize: 662204
[13-02-2015 18:53:25:612][..\..\..\..\..\..\LSFramework\Code\CoreLib\PackedFile.cpp 347 ls::PackedFile::Load]: Failed to load the pack file, Table Of Content is corrupt!
[13-02-2015 18:53:25:612][..\..\..\..\..\..\LSFramework\Code\CoreLib\PackedFileManager.cpp 214 ls::PackedFileManager::LoadPackFile]: Failed to load pak file: 'C:/Program Files (x86)/GOG Games/Divinity - Original Sin/Data/Game.pak'!
[13-02-2015 18:53:25:830][..\..\..\..\..\..\LSFramework\Code\CoreLib\PackedFile_TOC.cpp 109 ls::PackedFileTOC::LoadTOC]: Number of files in TOC larger than buffersize! Files: 4160749568, BufferSize: 7237444
[13-02-2015 18:53:25:846][..\..\..\..\..\..\LSFramework\Code\CoreLib\PackedFile.cpp 347 ls::PackedFile::Load]: Failed to load the pack file, Table Of Content is corrupt!
[13-02-2015 18:53:25:846][..\..\..\..\..\..\LSFramework\Code\CoreLib\PackedFileManager.cpp 214 ls::PackedFileManager::LoadPackFile]: Failed to load pak file: 'C:/Program Files (x86)/GOG Games/Divinity - Original Sin/Data/Main.pak'!
[13-02-2015 18:53:25:908][..\..\..\..\..\..\LSFramework\Code\CoreLib\PackedFile_TOC.cpp 109 ls::PackedFileTOC::LoadTOC]: Number of files in TOC larger than buffersize! Files: 1442841088, BufferSize: 1457684
[13-02-2015 18:53:25:908][..\..\..\..\..\..\LSFramework\Code\CoreLib\PackedFile.cpp 347 ls::PackedFile::Load]: Failed to load the pack file, Table Of Content is corrupt!
[13-02-2015 18:53:25:908][..\..\..\..\..\..\LSFramework\Code\CoreLib\PackedFileManager.cpp 214 ls::PackedFileManager::LoadPackFile]: Failed to load pak file: 'C:/Program Files (x86)/GOG Games/Divinity - Original Sin/Data/Textures.pak'!
[13-02-2015 18:53:28:482][..\..\..\..\..\..\LSFramework\Code\SteamBinding\SteamAPIManager.cpp 80 stm::SteamAPIManager::Init]: Steam must be running to play this game (SteamAPI_Init() failed).
[13-02-2015 18:53:28:482][..\..\..\EyesOfAChild\Code\EoC\App.cpp 892 App::InitCommunity]: Failed to initialize steam community
Shouldn't a corrupt TOC also make playing the game impossible?