Adobe Illustrator

Illustrator - Pathfinder Tools

Make sure to first 'Compound Path > Release' with paths that contain holes (e.g. letter O) before performing union with an adjacent path.  Use 'Minus Front' to clip the 'hole' paths from the resulting 'union' path.

Quark

Curved text paths and/or other advanced layout elements not saved or corrupted. In version 4.04 there is a known issue that causes it to save files in older version 3 format if an explicit save as version 4 is not done.