I have been running Ubuntu 12.10 on my laptop for quite sometime with no problems. Today I upgraded to 13.04 and had no problems until I used the Unity Tweak Tool to change the theme. I can't remember which theme I selected but it was one of the defaults and it caused my desktop to freeze. Now when I turn it on the login screen works but after logging in only the cursor and the desktop background appears. I can't even use the keyboard to open a terminal or anything and am stuck typing this out on my phone. If any of you have any ideas on how to fix this huge problem that has come out of nowhere, I would greatly appreciate it.