I messed up my system while trying to fix permission problems for setting up a LAMP local server.

I tried this solution: How to avoid using sudo when working in /var/www? without success.

Then I saw this solution: Permissions issue: how can Apache access files in my Home directory?

I understood that I had to change the permissions of my root directory (among others), so I executed: sudo chmod 710 /

I also changed the user group on / to www-data.

I also did these operations on /home.

I'm pretty sure one of those commands broke something, because it's the last commands I executed, and after that, my system showed strange/broken behavior:

• Firefox stopped showing pages
• Some icons got replaced by an red X icon (meaning "Icon not found" I guess)
• Applications refused to launch (no reaction)

After rebooting:

• I got a strange graphical message talking about not being able to mount something, asking me if I wanted to wait, and talking about /tmp (I forgot the message since I was in shock)
• My system now boots in console, and when I login, it flashes unsignificant stuff* before re-asking me to login.

My important data is on Ubuntu One. I'd prefer not having to reinstall from scratch. Is there a way to regain access to my system?

Thanks a lot for your help.

*Looks like a terminal header with the name of the OS and other info. Doesn't seem important.