What does the following message mean ?

PXE-E74: Bad or missing PXE menu and/or prompt information.
PXE tags were detected but the boot menu and/or boot prompt tags were not
found/valid.

We have this on several workstations. Imgserv & pxestart load properly. We
use the zen 6 suite on a nw6sp3 server.

regards,
Piet