Are there any completely silent tracks in your project. Steve says:
If there are, get rid of them and try saving the project or doing a Save As, or try the nightly build.stevethefiddle wrote:There was a remaining bug in Audacity 1.3.9 that caused the "disk full/not writable" problem when saving a project if the project contained any completely silent tracks. This has been fixed in Audacity 1.3.10 (available as a "nightly build" http://wiki.audacityteam.org/index.php? ... tly_Builds ).
Are there any illegal characters in the file name, as Koz asked? Probably not, if it worked before. But worth looking at.
In order to save what you've got, without saving the "project" as such, you can do an "Export Multiple" and choose to export one file for every track. That at least will get the work you've done safely stored away. If the project does explode, at least you'll be able to start a new project and import those AIFs into it.
Now, you said you got a new computer and had the projects on an external drive. This could be as simple (!) as a permissions issue. You don't say if you were trying to Save As to the external drive or your internal drive - the permissions are different. In any case it is worth doing a Get Info on the internal drive, Audacity Application, the external drive, one of the .aup files on the external drive, and any file you have successfully saved on your internal drive. Do that and tell us what you found - we're interested in the "sharing and permissions": who can read and write.
It might be worth starting up your new computer from the install DVD, starting Disc Utility and repairing permissions.
When you've tried these things let us know what happens.
-- Bill