Dear Mr./Ms. Face:
While Archicad is a complex and powerful software, (think of it as if it were "Stanley" in "A Streetcar Named Desire" (the movie version) where the character is complex and powerful but gets easily distracted or confused) it can get confused and unco-operative.
There are several graphic issues that require restarting Archicad:
1: loss of the selection box ants - as you note.
2: selection dots don't appear, yet the object is selected as indicated in the info box.
3: impossible hash of spider lines in the 3D window.
4: can't see elements as they are being drawn, but when clicking to complete the operation, they appear.
Just to be fair, these things usually only happen with two or more sessions of Archicad open and I get the feeling that I am running out of RAM since there are also another twenty applications open.
Dwight Atkinson