There is not one sure solution for these market related android errors and you'll have to try a bunch of fixes to fix these errors and chances are that the errors will come back and you'd have to repeat the process. The 911 error mostly occurs when you are trying to update your apps in the Google play store while connected to a faulty wifi network.
Method 1: Clear the Google Play store data
- Go to Settings >> Manage Applications or Apps >> Open "All" tab
- From the list of "All" apps >> Scroll Down and Select "Play Store" >> Select Force stop, Clear cache and Clear data
If you are using a wifi connection that requires a webpage login, then your authentication has probably expired. Log in to the APN again via your android browser. Open Google Play store and run the app update again . If that didn't work the problem is with the wifi network itself.
Simply switch to another Wifi network and run the update. The error 911 should disappear for the new Wifi network.
Use your mobile network data services instead of wifi. Turn wifi off and then turn your data on and now open your Google Play Store and download/update your apps or games. However, this method is only suited for apps and games that are small sized. For larger updates you should use your wifi network to save data charge.