Make the sure that the current version of SPS 1.0 is exactly the same one
available when you have backed up the sharepoint workspace. Make sure of the
services packs were installed at the backup  time.

I am restoring the backup  on the very same machine.
What I did was this:

1) I took the backup using backup wizard.
(successfull)
2) Deleted one document from the SPS 1.0 Doc Lib.
3) Run the restore  wizard to restore that document.
4) It said, Error restoring one or more files.

My Hardware configuration is as follows:

Pentium 3 Compaq Server, 512 RAM, Windows Server 2000
running SPS 1.0, Service pack 2a, Windows SP 4.0