1) Go to your phone's Settings > Storage

2) Unmount SD Card (your external SD card)

3) Download/install from the app(s) from the Store again

4) Go back to Settings > Storage - then Mount your SD card again (or reboot)

Or you can try this

1)Insert the sd card in you windows pc 

2)You will find a folder named `android_secure` in it you will find the file named `smdl2tmp1.asec` delete it

(Make sure in pc folder options, the `show hidden files` are enabled and the `hide protected operating system files` is unchecked)


Source: [XDA][1]


  [1]: http://forum.xda-developers.com/?__utma=248941774.1239869885.1394634270.1397478323.1397568266.7&__utmb=248941774.1.10.1397568266&__utmc=248941774&__utmx=-&__utmz=248941774.1397568266.7.7.utmcsr=google%7Cutmccn=%28organic%29%7Cutmcmd=organic%7Cutmctr=%28not%20provided%29&__utmv=-&__utmk=206227472