I started having problems (clean install of Win 7 Interpreise, and install of Live Writer) can't post and can't save drafts: Error accessing local post, IOException, There is not enough space on the disk.
This sounds like you might have a redirected My Documents folder ("Documents" on Win 7) to a location other than your local drive. If this is the case you would need to set it back to your local drive. If your redirect folder is off-line or you reach a disk quota you will see these type of issues.