Well, I can no longer check the SDI type. We have upgraded to 2007 and I have had no problems.
I discovered why my other problem occurred. Under Tool, option, system tab and general option, the single drawing compatibility mode was selected. I am not sure why this changed? I am the only using this computer and have been using it for about a year before this started happening. I did unselect it and it fixed that problem.
Sorry for the delay in my reply.