I have a 7920 with cmterm_7920.4.0-03-02 firmware, on a CME 4.1(0) router , IOS 12.4(15)T4 (previously was on 12.4(2)T with same problem).
The problem is the site has 10 phones, 8 7940s and 2 7920s that have all the lines shared between them (same button assignments). When line 1 is in use, all the wired 7940 phones show line 1 in use but the 7920s line show the lines are all available most of the time. Sometimes, rarely, the 7920 reflects the right line status.
Any ideas on what could be causing the 7920 not to show the right line status all the time?