PalmOS does not support Hebrew, Chinese, Korean, Czech, or Russian languages natively, but do so with the help of third party font-mapping utilities.
If you already are using one of these utilities (such as Penticon Hebrew Support, PiLoc, or CKJOS), make sure 'Fancy System Fonts' option in TealDoc's 'General Prefs' is set to 'None' or 'Auto', as third party font-mapping apps don't support custom fonts.
Also try turning off anti-aliasing in the TealDoc reading screen's font selection dialog if it is on.