Pro Tools Error..., I can't use the function 'bounce to disk' anymore... Options

[Welchownt]

Hye everyone... hope you 'r' fine: that's my big problem.

I use a dual core 2 2ghZ on a mac book. For a few days when i open a recent pro tools session this message appear :

"The original disk allocation for this session cannot be used. Check the disk allocation window to see what's changed."

And there some echoes on other applications like the function ' bounce to disk'. When i wanna use this one , Again i get a new error message : The page to save your record appear so you'll select and rename this one and when i click on save that message appear:

" Macintosh HD is not an audio playback volume".

So if someone could help me?

Thx