Hey got some updates about error 101. I have a rooted xperia play. First my encounter with this error started after downloading Brothers in Arms. In consistently gave me the error whenever I download any apps more than 24 hours. Then I realized that I've froze and uninstalled some bloatwares/pre-installed apps on my xperia, I have titanium back up (free ver) for unistalling and system cleaner for freezing apps. So I restored everything (not resetting to factory default), reboot my phone, then tried to download apps again, and it went back to normal, I was able to download apps again.
The only question here is which of the pre-installed apps that I blocked that cause the 101 error... Hope this helps, I'll try to see which app it is.