Flashing Defender Disabled message in Windows 8

Question

Windows

The day before yesterday I upgraded Windows 7 to Windows 8. For two days everything was fine. Today (seemingly after installing some system updates) in the notification area every 5 seconds a message about the disabled "defender" (windows defender) began to flash. The message appears and immediately disappears (I managed to read it by taking a bunch of screenshots). I have DrWeb installed (it was installed before the update) and the full-time defender seems to be disabled altogether. Has anyone experienced something similar?