[Asterisk-Users] Echo after asterisk has been running for several days

[Matt]

Hi,
I am running the latest version of asterisk.   (1.2.1)   When the
machine is first started, asterisk runs great and there is no echo.  
As asterisk is running for a few days (2 weeks or so) echo begins to
become more and more noticeable.

The echo is noticeable to both parties (both sides of the call) at
different times.  A reboot of the machine clears the echo for a few
weeks.

Any thoughts on what is going on and/or how to fix?