There is currently an issue with PHP5 and the myLANsite components for Mambo. It is all due to the one function:
mosMLS_events_participant::checkPaid()

I am currently working on this and will repost all affected components as soon as possible. Currently known as being affected are:
com_mls_catering
com_mls_seatmap
com_mls_tournaments

Apologies for any inconvenience. Note: This does only apply to PHP5. Everything works completely fine on PHP4 (or at least: it should).