Yup.
A narrow saddle can place stress on the sacrotuberous and sacrospinatus ligaments, which can yank on all kinds of structures within the pelvis and cause all kinds of havoc. (my personal theory is that this is where some of the "hysteria" over women riding bikes at the turn of the century came from)
Can you keep riding on the older, well-loved saddle on the new bike and see if it does the same thing? If it does, please go to you doc, the cause may be something else.
(so far you only have 2 data points, right? Both were races on the new saddle, so see what happens as you ride on the old saddle?)
Stress can also throw things off cycle-wise, and if you feel AT ALL that this might not be related to the bike and the sadde, please go to the doc ASAP!
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson