Domaing Mapping on a parked Domain

I have two domain names registered with my hosting company.
1) is the primary domain
2) is a parked domain

On my MU installation under, I created another site "" I would like to map '' to ''

I've gone through what I believe to be the correct steps.. but when I try to map the domain under the '' dashboard, the computer continues to process.. and never finishes mapping the domain.

Any guidance would be much appreciated!!

Best regards,