When the application is freezing, are you seeing any error message or is the application window just not responding (or showing a semitransparent white overlay) with a busy mouse cursor?
Do you have any background processes running that affect your user Documents folder, such as it being synced via Dropbox (or similar), backed up via CrashPlan or other backup program, or indexed via the OS? If so, could you try temporarily disabling or excluding the Documents folder from syncing and temporarily pausing backups to see if that helps?
Did this problem just start happening, or has it always done this?
Can you try creating a new project that's not within the Documents folder (e.g., just on your desktop) to see if that works, and Save As from that to another location (again, not within Documents) also works?
Thanks.