I have a 4 year old Colisanti White tree (in a pot) that provided a few ripe figs in 2010 and 2011.  This year it is loaded with green figs and I have been eagerly awaiting ripening.  A few started to turn yellow, never swelled and have fallen off.

What gives?  Too much water, not enough water?

Does not look like bugs or animals.

Thanks.

I had a couple fall off mine but most are staying on, and some starting to ripen main crop.  I am not sure if the dog pee played a part in mine or they got a bit dry a couple days or perhaps there was a few that weren't meant to be but I didn't find any reason why they fell off yet.

It is acceptable for young figs ,younger than three years to drop some fruits when in pot especially.
However the most reliable fig i grew,Marseilles black vs ,and JH Adriatic never dropped,and they fruited the first year from cuttings,i mean cuttings rooted in February,made ripe fruits in September the same year.
Not only that but when time came to harvest the fruits ,the tree hold on fruits,and they need to be cut off.
Holding on fruits, is the sign of a totally parthenocarpic ,persistent,Mama fig tree.