Hi
I have done some investigation and it seems that this is a general issue for many people. However after further investigation the issue, for some strange reason, only applies to certain font sizes. The problem font sizes are as follows:
Simplified Arabic: 8, 10, 11
Miriam Fixed: 10, 11
All other font sizes seem to display correctly. So if you can avoid using these font sizes it may resolve your problem. Sorry I can't be more helpful.
Good luck.
Tony(OTPM)

Thanks OPTM. It must be something in the font itself perhaps? I've experimented some more, and I'm seeing the problem for Simplified Arabic Fixed for font sizes 12, 11, and 8. And Mirriam Fixed at 11 and 8.