A 0755 should do the work, you probably are mixing it with ROFS (Read-only file system) issue that has struck most of the fellow x10 users.
Are you receiving a dialog box asking for "connection information" ?
If yes, wait for this ROFS issue to be sorted out and then try again.
If it fails, then take a backup of your current site and do the upgrade on your localhost(linux with 0777) and then upload it again(with 0755).
Merci !