I have the same problem... a dual signed app was unable to be authenticated and all other app's i run keep giving me a security prompt. I tried to install Y!Mail... authentication fail, Bolt Browser... authentication fail, Yahoo mobile... authentication fail, Opera mini.... authentication fail. I have a 4 GB micro-SD card installed and I get insufficient memory prompts at websites that I know I should be able to browse (some i have browsed previously). What is wrong with my phone? I have had this phone for 2 weeks and have had nothing but problems with it. Tried calling customer service several times, but get told I have to use a different phone.