From our techy:
They were on the right track: I got the search form working again - it was the directory permissions, not the file itself, which had the correct permissions.
Permissions differences are the primary source of problems when doing a transfer like this. Although I took great pains to compress and transfer the files with all structures and permissions intact, because of slight differences in the operating systems (one flavour of UNIX to another) the permissions settings did not stay the same.
The temp file itself is literally temporary and will be overwritten soon as people do more and more searches.
