Problems when i try to update the advance of one task

Hi Everyone.

I have a problem with my MS Project File, some task don't accept the value of the advance, if the actual value in the cell is 35% and i try to update to 50% or other value when the value is wrote in the cell... can occur one of this:

1. That the actual value stay and don't accept the new value...like the cell was read only.

2. That when te value was wrote don't take the wrote value, else in the cell appear other value different at the initial value and different at the wrote value...example, if the actual is 25%...and i write 35% appear 75%.

In a file whit 100 task, only 6 show this symptoms the others work normal...

How i can fix this problems, without rebuilt from cero the file cause the work have 8 months and we are close to finish (1 or 2 months).

Thanks for all the help.