Please describe how to replicate this problem.
For example I tested following code without problems:
// Save object with a buffer of 1000bytes
ImageEnVect1.ObjUserData[-1] := AllocMem(1000);
ImageEnVect1.ObjUserDataLength[-1] := 1000;
ImageEnVect1.AddNewObject(iekLINE, Rect(0,0,10,10), clRed);
ImageEnVect1.SaveToFileIEV('c:\test.iev');
// Load
ImageEnVect1.LoadFromFileIEV('c:\test.iev');