Incredible Bug after last windows 10 Update using Arial Font Corel 10 and Corel 6

Incredible. After last update windows 10, i have a strange problem in Coreldraw 8 and 6
Using ARIAL font

When i write the text ff the letter change in a ascii symbol square. This problem is only in advanced view and not in structure,

but only with small view. When i zoom in the ff show well. When i zoom out transform in square.
How is possible? And How i can solve this great problem