DMPfold error while running protein structure prediction
The comment by Devon Ryan is correct - looks like your blastpgp command is not working properly. For a protein of that length it's more likely to be a problem with the BLAST executable running on your system than a memory issue.

Try running the blastpgp command (https://github.com/psipred/DMPfold/blob/master/bin/runpsipredandsolvwithdb#L26) on its own and see what happens:

~/path/to/blastpgp -a 12 -b 0 -j 3 -h 0.001 -d yourfile.a3m -i yourfile.fasta