Thanks for the tips Helen. I'm using 1.5.2 (2005060220). You're right about the Apache version: 1.3.7 is the one I'm using. PHP (as found from the php info administration button in moodle) is 4.3.3. MySQL on my install is, as you say, is 4.0.15. I restore the backup zip as a completely new course. There are a total of 38 sco's within the backed up course, no user data or other activities.
I have more information: it appears that the scos are being zipped. Restoring creates a new directory in moodledata which in turn contains all my scos. In a moddata/scorm data theres a numbered directory corresponding to sco - they are being unzipped. I'm assuming this value is a primary key within a database (which one I have no idea). So, the sco's are being unzipped.
This may be more to do with the SCORM forum - I'm not sure. I can see the table of contents of a sco without any trouble at all. Clicks on TOC nodes which call 'playsco' javascript is what is causing the earlier posted error to occur.
A final comment: The sco's unzipped in my numbered directory doesn't match what I see on the php querystring, i.e., ...playscorm.php?id=153 corresponds to an entirely different object in my moddata/scorm directory to one that I would expect.