Minecraft 1.4.2, Minecraft 1.4.4, Minecraft 1.4.5, Minecraft 1.4.6, Snapshot 13w02a, Snapshot 13w04a, Snapshot 13w05a, Snapshot 13w06a, Minecraft 1.5, Snapshot 13w11a, Minecraft 1.5.1, Minecraft 1.5.2, Snapshot 13w18b, Snapshot 13w18c, Minecraft 1.6.1, Minecraft 1.6.2
Windows Vista x64 && Java Runtime Environment 188.8.131.52 (64-bit)
V-Sync does not retain settings between sessions in window mode.
Once V-Sync = TRUE in client is set, Minecraft will automatically apply. When the game is closed, and later re-opened, Minecraft will start without applying V-Sync. However, V-Sync will still show as 'true' on the video settings screen.
If the user toggles the setting, or switches to Full Screen and back. V-Sync will apply again, until the game is later closed and reopened.
Confirmed user has proper permissions to write to options.txt, Value of true is also being saved.
Setting Vsync as True in options.txt and opening Minecraft for Window mode has the same effect.
This affects existing worlds, and newly created 1.4 worlds.
Tried on a second Vista64 PC. Problem persists.
If Minecraft is set to use Full Screen, then V-Sync will automatic apply once started, if the value is set to true. This only appears to affect the default window mode option.