Thank you Chris. However this is a sad comment. It should be clearly stated on the monitor's specs that it is not tested with MAC instead of then telling customers when they have issues that it was indeed not tested with a MAC... Or the simplest thing to do is to simply test the monitors with the MAC in the future... . Hope that it is in Dell's upcoming efforts since although MACs users are not as widespread as PCs' I do beleive they represent a certain portion of Dell Customers and ignoring MAC users is no good.
Thanks again for the help. If anyone has similar issues, please drop a line.