[Occurs when trying to update an existing application]
If you receive this error, try deleting the original...
(Pay attention to page/placement, as you may need to move it to its original location manually.)
First, clear the dialog box, click 'Done', then press and hold your finger on the icon until it starts to "jiggle", press the little 'X' in the upper left corner of the app to delete it.*
Tap the icon again to install it.
Press and hold your finger until it starts to "jiggle", then hold down the center of the icon and drag it to the right edge to move it to another page.
*Apps from Apple's App Store only.
(Cydia and Installer apps, delete through those programs -where it was downloaded from.)
