This is a bug in the new CC 2015 release. Please fix. Thanks.
That's not much use without some proper system information and other technical details to put it in context.
This is a known bug, and recoverable without restarting. See "scrubbing audio causes the CTI and PTI to disappear" here:
known issues in After Effects CC 2015 (13.5) | After Effects region of interest
The After Effects CC 2015 (13.5.1) bug-fix update is available, which fixes this issue: http://adobe.ly/1Il5JYe
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