I ran into a very annoying bug: one very specific line in the list of my entries is always € 600 off and adds that amount to the preview sum. Interestingly enough, it doesn't matter what sort of entry is located at exactly that line. The sum in the account-overview in the sidebar on the left shows the right amount though, so the € 600 extra is only added in the preview-sum within the list of transactions.
I tried deleting that row. Then the extra € 600 are added with the entry that moves up to this line position. Changing the amount to € 0 in this line still adds € 600.
I attached a screenshot showing the mis-calculation happening.

85.185,10 + 5.856,00 ≠ 91.641,10
I hope this bug can be resolved.
I'm using iCompta 4.0.11 on a Mac running OSX 10.8.5