CTB file - compatibility problem with autoCAD

I installed IntelliCAD pro 6.6, with a regular license.
I realized that if I change the CTB file, the other colleagues who have autoCAD can't see the file CTB modified.
To view it, they should open with double click (start program styexe.exe) and save it again.
Only at this point they can see the ctb file in autocad.
All this is normal?
Do you have an idea to resolve this problem?