It is going to rely on two services on the local PXE representative.
- LANDesk(R) PXE MTFTP Service
- LANDesk(R) PXE Service
These will need to be on the PXE representative under Services.
You may want to try re-installing the PXE representative. Ensure that a PXE representative exists on the subnet your client is on.
Here is another possibility: http://community.landesk.com/support/docs/DOC-1230
Make sure your network switches aren't blocking TFTP or MTFTP. TFTP is on port 69.
Depending on your exact error, the solution may vary.
Here is another article you may want to look at:
http://community.landesk.com/support/docs/DOC-1143
What is the exact error you get?