There is a bug (or a limitation) in the Driver Setup rule that will cause this (or a similar) problem if there are too many drivers in the rule. Exactly how many drivers are "too many" depends on many factors (one of which may possibly be the phase of the moon).
The workaround is to split the drivers between two copies of the rule with the second copy as a child of a wait rule set for a delay of a few seconds.
Your problem, of course, may be totally unrelated to this.