If you lost the email, I prefer to repost my answer here, so it can be reused by other users:

You must be running Sweet Home 3D on a computer that uses a remote profile.
Maybe there's not enough room on the remote place.
To change the place where work files are stored, you should create a text file named SweetHome3D.l4j.ini in Sweet Home 3D installation folder, and put the following text in it:where you replace C:\absolutePathToWorkFolder by a folder where you know you can write.
Hope you can do it.