Getting "not enough space" error even i have enough space in sd card
Have you ever been able to download apps directly to your SD card? I believe the reason for this is that you can only install apps onto the internal memory; not any SD cards. I think you can only move apps after you've downloaded them. If someone can confirm that this is the case, see if you have any images or videos that you can move to the SD card to allow for more space inside the internal memory? Let me know how you get on :)

p.s. I also think the write disk system only works for pictures and the sort.