I know I am not current so don't get technical support but this may help others (if it hasn't already been fixed).

ACP picked the next target from my plan, identified it was below the horizon BUT still tried to slew to the target. Result was script failure. Would have ruined a nights imaging if I hadn't been monitoring it (only lost 15 minutes)

Log: http://www.david-higgins.com/20100703.zip