I don’t know how to fix this… but I can tell you that I’ve got my home folder on a different drive, and everything saves just fine.
Have you repaired your permissions?
If so, have you checked your write permissions for the appropriate folders?
If not, and if it turns out to be what’s wrong, BatChmode (google it) is a free utility that’ll straighten out that issue (be careful with it!).
I had to use it once to reset writing permissions for a DAW computer; it fixed everything up.
Chewy