4.0 ice cream sandwich - Memory settings menu inconsistently shows internal storage half-empty and completely full at the same time

I own a sony xperia tipo that has around 2 gigabytes of internal storage.

Today, I got a warning that my phone's internal storage is full, while using google currents, so I went to the storage menu in the settings, to take a look, and I saw that the calculated amount of used memory in the internal storage section was a tiny bit over 1gb. This didn't sit well with the fact that the reported free space was only 2mb instead of one giga and a half, as I thought it ought to be.

Trying to update apps that reside in the internal storage fails with an "insufficient memory" error.

I have no idea about what the problem might be and how to solve it, but I would like to try and avoid a factory reset, if that is possible.

Any help is greatly appreciated and thank you in advance for it.

EDIT: Here are two screenshots where you can clearly see that the total used space and available space do not add up to 2.15GB as they should but are only around 1gigabyte.

I have no idea what could be responsible for this phantom gigabyte, but one would think that the amount of memory the OS uses would have been subtracted from the "total space" and from the "phone memory" entry (not shown here) instead of the internal storage.

(I removed some apps to free up a few megabytes of memory)

Answer

Your phone keeps the thumbnails of all the photos that go through your phone. Connect it to your computer and delete all the contents of the folder called ".thumbnail" in the internal storage. You should find that folder inside the DCIM folder.