This is a common issue when attacking 'Storage Tank' targets. If it happens when attacking another type of target - airfields/flak/etc please let us know.
In the case of Storage Tanks - it is a video/gpu 'overload' due to smoke particles in CloD being just that - particle based. In CloD each 'particle' of smoke is being drawn and tracked - massive GPU load. The clouds in the sky, as an example, are instead 'volumetric' like how most other games create 'smoke effects'.
To get round this, reduce the 'visual effects' level to 'medium'. Lower than 'medium' will result in missing out on alot of effects and should be avoided.
Clicking the above thumbnail will give a larger image.
I hope this helps,