To reproduce this bug:

1. Open the attached project
2. Open 'test' scene
3. Make sure both text fields have 'a' letter inside them
4. Select 'georgia' font
5. In the import setting change Character to Custom set
6. Enter letter 'a' to Custom Chars field
7. Select one of the Input fields
8. Enter random letters to it
9. Select georgia font again and set Characted back to Dynamic
10. Notice some corrupted looking text in the input field containing 'a' until it refreshes

Captured reproduction for clearer steps: http://screencast.com/t/MRatWpV4e