Verify only one version is currently loaded and the memory has been defragmented as the memory can only store a maximum of two versions of code at a time. Delete one version if necessary and defrag the memory.
Verify TFTP syntax and IP address. (use -i for binary)
Verify proper file is used for the type of equipment.
5000load.bin for DS100x, DS500 and DS5000
alfload.bin for DS1500x