It's dependant on a couple of things (minimum).
1. the version of Quark. Each has it's own unique "issues"
2. The environment (i.e. single workstation, multiple workstation)
3. The font management software (if any).
The issue with v7-7.3 is and was, the application randomly "assigns" missing type (that really isn't missing) to a new face. If you're using any variation of version 7, you need to update to 7.5 (that's half the battle).