Re :Fatal error: Undefined class name 'db' in /tiki/db/tiki-db.php on line 67
I have no such file.
If I remember right (maybe 60% sure), I often (always) got that too installing. At least, other had the first line for sure. Look a bit and you might find.
If Tiki works, and you don't want to debug, don't mind 
;){kind=link}
;){kind=link}