Blender Git Commit Log

MultiSample feature: added provision that requires a restart in order to get
it work properly - you cannot set/disable it in a running program with windows
open.

In short: Multisample setting is static, set on first time running of Blender,
after reading the user preferences.

For as far as I can see - disabling/enableing (glEnable) doesn't harm to be
used in drawing code. With multisample on at start, you can enable and disable it
freely. But without it set at start, enabling doesn't do anything nor draws badly.