Same problem for me, I can play for 5-10 minutes, and then it crashes... Tried to remove autosave as well, without any luck. Mac OS X.
"Savegame::Load: ERROR: File is not a valid RTTR savegame!
SavedFile::Load: ERROR: Old file version (version: 25; expected: 28)!
Savegame::Load: ERROR: File is not a valid RTTR savegame!
SavedFile::Load: ERROR: Old file version (version: 25; expected: 28)!
Savegame::Load: ERROR: File is not a valid RTTR savegame!
SavedFile::Load: ERROR: Old file version (version: 25; expected: 28)!
Savegame::Load: ERROR: File is not a valid RTTR savegame!
SavedFile::Load: ERROR: Old file version (version: 25; expected: 28)!
Savegame::Load: ERROR: File is not a valid RTTR savegame!
SavedFile::Load: ERROR: Old file version (version: 25; expected: 28)!
Savegame::Load: ERROR: File is not a valid RTTR savegame!
SavedFile::Load: ERROR: Old file version (version: 25; expected: 28)!
Savegame::Load: ERROR: File is not a valid RTTR savegame!
SavedFile::Load: ERROR: Old file version (version: 25; expected: 28)!
Savegame::Load: ERROR: File is not a valid RTTR savegame!
/Users/ahembre89/Desktop/Spill/s25rttr_20151217/s25client.app/Contents/MacOS/rttr.command: line 63: 2522 Abort trap: 6
./bin/s25client "
Any suggestions? :)