[Q] Help ...Apps not getting installed

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http://forum.xda-developers.com – I have just rooted my phone and tried a couple of ROMs...CM9.1 with Siyah kernel and just yesterday installed the AOKP JB (attaching screenshot with the current config of my phone. The problem with both of these has been that I am unable to install most of the apps from apk. After i click the install button, i simply get a message saying app not installed (attaching screenshot) Pls help. Havent been able to find any solution by searching online. Unknown sources is checked... Attached Thumbnails     (HowTos)