I have the same problem...it seems the problem started after I put in the credit card NO. to the free -Apple ID.
At first I was using ID for free downlaod app ( no input credit NO.) that period I just click on buy app ( paid app) to see what will happen..... ( sure it didn't let me download cause I didn't credit NO.)
at last...oneday I decided to buy a paid app....so I update the same old APPLE ID with my credit card NO.
After that I got error message... " the app xxxx unable to purchase this time..."
Well...it 's the name of paid app I click to test to downlaod (while no credit card) ...:( I didn't really want to buy it... but it still randomly pop up when I try download any new app.
More over.... I got another error... there's an free app I try to download ...and I stop process before it complete. SO when the error meesage pop up.... the error download icon is show up in my ihpone too! and I can't delete it ....it's the icon app..showing in " waiting " stage. I just have to open another app or download new app to make it disappear. but It can comeback again !
Finally I try new way...hope it works permanetly.
I open Itune on PC. conenct to iphone.
- go to iTune store > log in APPLE account > choose your account -name on top right. > click it and put in password again
- You will go to Account information page...look down and you will see tab " reset warning all buying and download item"
click it and sync iphone again...
I think the problem is gone now...but have to try again tomorrow if this will permanently work....
please try my way and tell me how is it....