Just started experiencig this bug, just in time, 3 days till deadline.

Happens randomly, on random files, mostly on project open while it converts materials for viewport.
Sometimes it will crash octane plugin too.
Tried updating gpu drivers, got new octane version, no luck.
There's a pic in attach how the viewport will look like after this issue and followed plugin crash.
Bugreport is also there.
Octane v2.25R3
Gpu v361.91 2xGTX770
C4D v17.048
Win 8.1