asterisk users - Jan 2007 - TDM2401 (FXO) Hangup

Anybody else having trouble with hangup detection on the TDM2400 FXO
modules? It works most of the time, but sometimes I get hung lines in
Voicemail. And only with the TDM24xx not with the TDM400 or Adit 600
CB. Anybody else have this?