Good morning, Cheri.
This is the first instant-replay dream I've received since putting up the page, so this is a bit of a challenge. Let's see what we can make of it, starting with the familiar.
Driving anywhere with someone is usually a comment upon the relationship. It's helpful to notice who is doing the driving - this is the person you feel is "in charge" of the relationship.
The road you're on is near your house. This points toward an issue "close to home" -- something very important to you.
If you go through the same events more than once, with changes each time, this would seem to represent a choice, each replay and each difference indicating the complexity of the choice at hand. You have only one replay, and one difference, so your choice is fairly simple.
So now we need to look at the man walking the dog. As a generic symbol, this can indicate someone minding his own business, or it can indicate friendship (man's best friend). The two are not mutually exclusive - it can be a friend who's minding their own business, for instance. In the replay, the man is dead - you didn't say whether the dog was dead, too, or even there. This might suggest the end of a friendship (possibly the result of not minding their own business?).
So, what I get from this is, you have a choice whether to keep a friendship alive. The choice has something to do with your current relationship with your boyfriend, but doesn't require ending that relationship - it seems to depend more upon the actions of the friend.