Are they always the same parts?
If so, my bet is that someone has edited the assembly template and saved it with those parts assembled to it. In our setup, it is called:
2014 assy temp.asmdot
Yours could be called something else, but its filename will end in 'asmdot'.
Edit the template, delete the assembled parts and save it as an empty assembly template.
Ours is in a common network directory, with the prtdot and drwdot files, and they are all locked down as Read-Only, to prevent just such things occurring.
Try that for a start.
Thank you! That fixed it!