LTSP fails while downloading images

Some time ago, I've configured LTSP on Debian machine. I've been using it from time to time and it worked. Today it stopped working and I cannot figure out what's wrong. Client says: Intel UNDI, PXE-2.1 PXE Software Copyright (C) 1997-2000 Intel Corporation Copyright (C) 2010 Oracle Corporation CLIENT MAC ADDR: 08 00 27 06 AB AB GUID: 8E607128-4C80-4960-BF72-347FDBDB27B5 CLIEHT IP: 192.168.1.163 MASK: 255.255.255.0 DHCP IP: 192.168.1.1 GATEWAY IP: 192.168.1.1 PXE-E35: TFTP read timeout PXE-E39: TFTP cannot read from connection PXE-MOF: Exiting Intel PXE ROM. FATAL: Could not read from the boot medium! System halted. I took a look at server's log, but tftp's logs doesn't seem to be useful: Dec 7 22:44:25 Serwer in.tftpd: RRQ from 192.168.1.163 filename /ltsp/i386/pxelinux.0 Dec 7 22:44:25 Serwer in.tftpd: tftp: client does not accept options Dec 7 22:44:25 Serwer in.tftpd: RRQ from 192.168.1.163 filename /ltsp/i386/pxelinux.0 (those messages above are generated by tftp with --verbose mode). So it looks like I've a connection from tftp clients to server, but why did it die? I could not find any way to see more log informations.