The Asterisk development team has released version 1.4.5 of libpri. This release was made solely to correct a problem introduced in version 1.4.4:
In February of 2008, a change was made in libpri to support inband audio (progress) when the far end of a PRI circuit issues a RELEASE message, indicating they want to terminate the call. This change was necessary for some applications where the telco providing the circuit wants to provide a 'release message' before actually hanging up the call. Unfortunately, many users have PRI circuits that are not compatible with this behaviour, and this results in their PRI B-channels being left open for anywhere from 2 to 20 seconds (or more) before the calls are finally terminated.
This version of libpri retains the ability to operate in this mode, but it is now a configurable option which defaults to being 'off'. The next releases of Asterisk will have configuration options to turn this behaviour on if the user desires.
Thanks for using libpri and Asterisk!