Does undergrad score matter very much when applying for a second Masters?
Your question is difficult to answer confidently because you don't provide information about the program you're interested in or your prior studies. What did you study in the past? What do you want to study?

Did you do well in your undergraduate classes relating to your prospective masters area? Is your most recent masters in an area closely related to that of your second masters? Did you perform well in your first masters program?

To make things easier, you should perhaps call the admissions office of the program/department you're interested in joining. Be straightforward about your situation and they'll likely be helpful in guiding you.