Fix a couple of Magento bugs

I'm running my e-commerce project on a magento website. We just upgraded to 1.7, and installed a new theme. The main functions of the website work perfectly fine, we proceed orders, etc. However, we encounter a few bugs : 1 - The categories section is having a problem : all categories fields appear to be empty when you edit them, yet categories are full in the Database. This is a problem, because we can't edit the categories content through the Admin (Title, description, meta, etc..), only through phpmyadmin. Also, the navigation depends on the categories information. When we try to fill the category fields and save, magento creates a new root category with the same name, empty as well, and doesn't edit the current category. 2 - We selected "french" in the admin backend view, but everything is still in english 3 - We can't switch between store views when editing products. It would always jump back to default. Tech details : Our website is hosted on a private Linux (FreeBSD) server. Which means you will have access to PHPMyadmin, SSH commands, SFTP, but there is NO Cpanel and NO client graphic interface. If you're not familiar with FreeBSD, Debian, and private host without graphic interface, then please don't bid.