i'm having the same problem as the person in this thread http://www.simplemachines.org/community/index.php?topic=412511.0
it says
The upgrader was unable to find some crucial files.
Please make sure you uploaded all of the files included in the package, including the Themes, Sources, and other directories.
I tried upgrading twice and I get the same error both times even though I uploaded all the files and changed the permissions on the directories/files I was supposed to but I still get the error.
what files are you uploading? are you uploading them to the correct folders that they came out of?
When I solved that topic, it was simply that, as Illori has asked you, the files were in the wrong directory.
Do you have httpdocs and all that crap, or public_html?
i figured out the issue, some of the files didn't upload correctly, so it's solved now. Thanks for trying to help though.
(https://www.simplemachines.org/community/proxy.php?request=http%3A%2F%2Fwww.katzy.dsl.pipex.com%2FSmileys%2Fc014.gif&hash=f74820123053ff9301b57a2ded5672bfa96b900b)