No higher Interrupt can change the variable, because the assignment to a temporary variable is protect by the EA=0; EA=1 statements.
(At this moment, there is no higher Interrupt running too!)

But your first mail shows me a possible reason.
When i disable all interrupts with EA=0 inside the I2C-ISE, and a change of the SCL line occures, before i reenabled the interrupts with EA=1, can i loose this event???

Gruß
Markus