This is the first I had heard of EG 4.21... so I did a little investigation. Based on the following, it looks like there are four problems that are dealt with. The only one that looks semi-major is that projects created in 4.1 were apparently not maintaining the grouping in Query Tasks when opened in 4.2.
Per Tech support: EG 4.21 is the current shipping release of EG. The only difference between 4.2 and 4.21 are localization/language updates (4.21 has additional language support not available in 4.2). --Doc