Heh, well that's rather strange. Usually that message appears when you've synchronized two waypoints with one another; i.e a Get In and a Load, two Move waypoints or somesuch. It'll disappear as soon as both waypoints are reached & the next one starts.
Possibly, this also works when there's something else stopping you from moving onwards, i.e the death of enemies (waiting for the enemy to die...).
As to getting rid of it, hm, I'm not sure. This is just a suggestion (OFP is not available to me right now), but try putting the wp condition into a trigger(a/b=0, type: switch, condition: not alive enemy1) instead, and synchronizing (F5, drag the line between the wp and the trigger) them with one another.
Might remove the message, and will work in the same way. Try it! Let us know if it doesn't work...
Wolfrug out.