Premiere Audio Capture Failure

[Patrick Masterson]

We are running Premiere 6 on Mac G4's for senior video production
students at the community college level.  A problem that recurs often
is that the capture from a Digital camera, either Canon or Sony,
sometimes works but only the picture is captured.  If a new project is
started the problem disappears.  Only the original project is affected
this way and even it did run fine up to then.
Our students and frustrated staff would appreciate any suggestions.
Pat