Make sure you have the latest version of Messenger Plus! (3.00.92) from www.msgplus.net
There is no compatability issues with MSN Messenger 6.2.0133 and Messenger Plus! 2.54.75 and above.
EDIT: by the way, open the Contact List, click Plus! > Preferences and go to Contact List on the left, then make sure "Hide the advertisement banne" option is turned on