I really do not see how running this on the server is going to fix an isolated error on a single machine.
Besides that
1. Office is not installed on the server.
2. SPD is not installed on the server.
3. Unless I am missing something I do not see an option to run office diag in SPD on my local machine.
Either way I have run the Office repair on the machine that has been having the problems and we shall see over the coming days if this resolves the problem.
D