Hello! Also appeared to me that problem when I had enough memory , I was researching my cell phone and I noticed that in Settings -> Application Manager the amount of memory to reserve the device applications appears in the blue bar below . Search the internet and found a forum that had that problem, a post that said to solve the problem and dozens of post of thanks to the latter . I put it into practice and ... I understood the truth because much appreciated . Knowing is stored in memory is not required logs that occupy a lot of memory over time. If you have no problem with the English , you make a copy and paste and try it :
Factory reset is not Necessary . You just need to do the following.
Just dial * # 9900 # on the phone and select option 2 "Delete dumpstate / logcat " in the menu to prompted .
This will restore heaps of storage space by deleting all the log files in the device memory . It's Not necessary to root your phone either.
and the dnd link I found :
Good Luck!