WAIT! WAAAAIIIIT A MINUTE!!! You did add all the starts you need, but DB deletes them. Then, it destroys all the stuff you make. AS IT SAVES YOUR MAP. That way, when you load it into SRB2, you get an error message with no player starts. Even if you did get a player start, you would have an empty map on your hands. Next time you load it, tell me how many lumps are in the file. If it is 1 or 0, it's a problem.
Try re-installing DB, and see if that helps.