There was a bug in the difficulty display in some previous versions.  The actual difficulty was always right, but it was reported incorrectly.  This has been fixed in recent versions.  Update your nodes, and if you mine for a pool showing 1779163, pester the pool operator to update his.

simple explanation:

0.3.20.2 calculates less accurately => 1779163.94366
0.3.24 calculates more accurately => 1777774.482

they must have been grabbing the difficulty factor from an older install temporarily.

edit: sorry i just noticed kjj said basically the same thing above.