I have a system that exceeds the official optimal hardware configuration. Patched and recent versions of video drivers ( Nvidia ). Game video settings are at default levels +/- one step.
1. When you create a free-floating cloud and back away to some distance, the cloud disappears. But moving back within range does not restore the cloud.
2. If you have too many (?) particle generators running A2 will begin removing existing cloud effects on a first-in, first-out basis. I was able to reliably create this phenomena with the new version of the ACE nuke. It created the mushroom cloud fine, destroyed about 12 vehicles in the test region ( setting them on fire ). But when sectional damage system was enabled and some nearby buildings collapsed, the mushroom cloud and rising column were zapped. Turning off the sectional damage allowed the mushroom cloud to behave as expected.
This is not an ACE issue, I'm the author of the graphic effects involved. It just seems like the game is hitting some limit in rendering at some unexectedly low level.