Android APK file installation error

[Tuts]

Hello,

I recently purchased a Sony Xperia U for Android development and I'm having problems with .apk file installation. I've installed Astro File Manager and I've comfortably transferred the file from my machine to the phone. However, when I click to install it, it comes up with the error 'Application not installed'. Does anyone know why I'm receiving this error?

I've got two versions of this application and when trying to install the first, I got the same error. However, after three attempts it installed.

I've used Google to try and diagnose why I'm receiving it but there are so many ambiguous answers. Thank you for any feasible answers.

[Jack!]

So you are long pressing on the file, then clicking open with package installer, correct?

I would recommend trying ES File Explorer, just to see if it still does it, its an interesting error for it to not work a few times,then suddenly work.

[Tuts]

After your suggestion, I installed three different file managers and I'm still getting the error.

I've tried adding the following to my Application Manifest

android:debuggable="true"
Still no joy.

For installation I am merely clicking the file. When a pop up is displayed asking whether I want to install it I click yes and then get the error. I've even tried testing the out of the box Hello World application and that too won't install.