I am sorry but i really don't understand why i get these nebulos errors. I did everything i read in readme file and on this forum.
Try deleting the entire themes directory and upload a clean fresh copy from the original installation zip file :P
It doesn't help, please help me fix this BUG!
I would like it if you could provide us your SMF Version :P
It was 1.1 RC2 and i downloaded upgrade package from this site. I copied everything like it suppose to be and entered www.my-domain.org/forum/upgrade.php into my browser. Then i got that message.
Then try uploading it via a different client such as filezilla :P, usually the client can mess things up and usually does :D
Sorry, i fixed the problem by editing setting.php and setting english as default forum language instead or serbian :-X