I've had this Miata for about 13 years and never had this problem. On a road trip, I stopped by the side of the road. When I jumped into the car and started it, I found I couldn't move the car forward in first gear; the car would stall. I couldn't shift into any other gear besides first and second gear. With the shifter in neutral position, the car would go in reverse.
I had it towed to a GM dealer (hey, it was a small town) and after taking it apart, they said that someone (ie. me) must have shifted the tranny into reverse and then somehow tried to shift into first. The result was that the transmission was actually in reverse while the shifter was stuck between what the mechanic called "the rails". The guy put it all back together and it works fine. There was no apparent wear, broken or loose parts that would account for this.
Has anyone had any similar problems with old Miatas?