Sorry, I can't think of anything else to do except a factory reset. Note that this wipes the phone of all apps and data, and if the phone restarts, you'll be prompted to reset as if the phone was new. Use the same procedure that I listed above (hold "X" while powering on, press both volume buttons) but choose the option "wipe data/factory reset".
You can reinstall all of your apps by using a PC browser to go to https://play.google.com/apps
(after the phone is activated on your Google account) - you can install them on the web and they will install on the phone over the air within a few minutes.
After you get the phone running, you would want to connect it to your PC and choose to mount the phone to your computer to look at the internal storage. If there is no space left, you'll want to remove some of your files to leave some space.
If this doesn't work, please reply.