You do not have mod_rewrite installed or properly configured on your server, because I get 404 error when going to other pages rather then index. 

Besides that, the following folders, should have permissions 777 set recursively: 

ow_pluginfiles

ow_userfiles

ow_smarty/template_c

ow_static

then rename ow_logs folder to ow_log and set permissions 777 as well

Thanks. I got it working in a minute, two things wrong with .htaccess.

I see you have 1.8.0 running now, looks like update was successful. Is your issue resolved or not?

I consider this resolved.

Note to myself: check .htaccess content, 777 folders: 

ow_pluginfiles

ow_userfiles

ow_smarty/template_c

ow_static

ow_log

Great, thanks for letting us know