Version 3.0 or higher
On the main menu, choose ReSharper | Options. Expand the 'Environment' node, click 'Products & Features'. Select/clear the 'dotCover' check box on the 'Products & Features' page of the 'Options' dialog box.
Older versions
On the main menu, choose Tools | Options. Expand the 'dotCover' node, click 'General'. Click 'Suspend Now'/'Resume Now' on the 'dotCover' page of the 'Options' dialog box.
You can also map any keyboard shortcut combination for the 'dotCover_ToggleSuspended' command (see Tools | Options | Environment | Keyboard).
This is now ReSharper | Options | Environment | Products & Features