The IOF has published revised competition rules for mountain bike orienteering, to apply from July 1st, 2008.
Changes are generally minor, and are noted on page 30 of the new rules. Perhaps the most significant is new rule 24.9 (The results must be based on competitors’ times for the whole course. No changes may be made to these times on the basis of split times).
The rules are available from the at IOf website.