I thought it was a little odd that my last flare happened right before my time of the month. In fact, I always get more symptomatic right before my period starts. Turns out I'm not the only one.
http://www.mscare.org/cmsc/images/pdf/07Houtchens%20.pdf
Evidently hormone levels have a lot to do with symptoms - low levels means you're more susceptible to relapse and pseudo-relapse.