Yeah, everything is pure speculation at this point. Their reported position on the reef some 4,400 ft (2/3 of a nautical mile) south of the middle of North Bar Channel is quite a ways off. Don't know how to explain that, really. Maybe a navigational error? GPS datum error? Don't know what charting system they were using.
My guess (and it's only that) was that the boat was swamped trying to enter the channel to the north and was driven south from the channel and onto the beach/reef by the swell/breaking waves. There is a transponder on each boat that has independent battery power and it so the current position shown on the Carib 1500 website is probably where the boat came to rest.
Here's the most recent data from Rule 62s transponder:
Richard & Debra Ross, Jeanneau 45DS
N26° 22' 41.2" W76° 58' 49.2"
2010-11-15 15:54:57 UTC -4h
0.0kn = 0.0km/h = 0.0mph
4.6kn = 8.5km/h = 5.3mph
831.9nm = 1540.6km = 957.3mi
637.6nm = 1180.8km = 733.7mi
Given that the time stamp on the position is less than an hour old, it's safe to assume the transponder is still operating and that the boat is currently at rest (Last speed: 0.0 kts) on the reef / beach.