Why do I get note entry and tie erros after time signature change?

Notion 6, Dell PC WIndows 7 64 bit

After a change of time signature from 4/4 to 3/4 or 6/8, note entry still acts as if the time is 4/4. It allows 4 beats worth of notes to be entered, but flags those past 3 quarter notes in red. Also, ties over a bar-line don't appear correctly after such a time-signature change. Can I fix this?