I have just tried to install an updated app using an apk file. All seemed to go ok, I was asked all the usual questions about installing over the original copy etc. During the installation however, I go the 'Application not installed' message but the app still ran ok. Thinking that perhaps the app could not install over the original I un-installed the original but now I get the 'Application not installed' message every time I try to install either the original apk or the new one. What's going on?