It is not the number of calculations, it is a loop that causes the problem. For example, suppose you have two fields, field1 and field2.
If you say "field1 = field2 + 1" and "field2 = field1 + 1", you've got it. It is just two calculations, but they call each other infinitely. You start with field1 being empty, field2 becomes 1, field1 becomes 1, field2 becomes 2, field1 becomes 2 etc...
when field1 becomes 16 and field2 becomes 15 InfoPath decides something is wrong and stops.
If you look at logic inspector, you will just see those two calculations so it doesn't automatically tell you that there is a problem, you need to figure it out for youself.
Note: you can make the example even easier... just set field1 to be itself + 1, you'll get the same error.
David Airapetyan / Software Services ArchitectQdabra® Software / Streamline data gathering to turn process into knowledge