I had 770 MB of space shown as "Others". I recalculated and found out that apps-1.49 gb space shown is apps installation space .It is not the extra space used.The extra space used by apps is shown in "Others",which was about 200 MB. Emails, browsing,cache too take up some space .When I deleted them (full email account), I was able to free up 150 MB of space from others and the new space taken up by Others is now 590 mb (200 mb of space by apps included). Restoring temporarily solves the problem.Try to find out the unaccounted space encroached by apps , emails, browser , and cache.
Yes I could not free up the space from "Others " fully. But somewhat I could.
So before restoring try some tweaks, as given by the forum users ,and look into the apps and email.They take up extra space and you will never know but "Others" will give you a hint.