i would bet that a connection string is incorrect when it is moved to production...
I don't know your app of course, but if the connections string is hardcoded to look for a specific machine name, ip address, database name, then it might fail;
check the basics of the connection string:
from the production machines perspective,
does the server exist?
database name exist?
user exist?
user have permissions to the database in question?
user can log into the db From query analyzer with the password supplied?
Lowell