If this a v1.2?
There was a problem with 1.200 in that for options products it set V_DownloadType to null. This could be later corrected by going in to edit the individual version concerned, and saving the change, but obviously that is not a good long term solution (and you'd end up forgetting to do it).
It was patched in later versions of 1.2 but there was a patch you could easily apply to the db to fix this issue (and hence not require an upgrade to a later 1.2. Its in the stored procedures...
go to _spKartrisVersions_Add and add this before the Disable Trigger line:
IF @V_DownloadType IS NULL or @V_DownloadType = '' BEGIN
SET @V_DownloadType = 'n';
END;
This won't fix existing versions but will affect later ones from being created with the wrong setting.
You should be able to execute a simple query to fix existing versions... eg
UPDATE tblKartrisVersions SET V_DownloadType = 'n'
If you aren't running 1.2, then it must be another issue.