If this is the case, there's a correlation mismatch. If an event is assumed to be correlated with the rising of Venus (a predictable, cyclical occurrence), but it's actually correlated with a random event such as a meteorite, then we have a problem.
Add this to a mismatch of solar calendar dates between Mayan sites and the end date of Dec. 21, 2012 could be at least 60 days out.
Aldana presents several reasons why the GMT constant may not be reliable, and he's not the first to do so, but he does admit that it is widely accepted by the majority of researchers. A lot more work (such as supportive radiocarbon dating) therefore needs to be done before his findings can be corroborated.
This is a fascinating area of work, but it is overshadowed by the inane ramblings of doomsday advocates who have their sights set on the world ending on Dec. 21, 2012. Alas, I doubt that even if this infamous Mayan calendar end date was proven to be inaccurate, doomsayers will ignore this fact.
After all, proving that the world isn't going to end is bad for business if you have a doomsday book to sell.