ImgX is middleware used by PartyCAD to manipulate images and is important to the functioning of many areas of the program.
Other software uses ImgX as well, and under some circumstances may remove it or replace the version supplied with PartyCAD with an older, unusable version. If this happens, you will start getting messages in PartyCAD referring to the problem.
The fix is easy and will not hurt your data, but it does take some time. What you must do is reinstall PartyCAD, which will also reinstall the correct version of this important component.
For installation instructions, go here.