Error message for pdb files

I got error message after submitting the job. Can anyone help me to understand the error message better and what should I do to resolve it.

Here is the message:
First pdb file contains multiple forms of the same residue. This is not supported in the current form. If you would like to supply multiple conformations, please create an ensemble
ATOM 330 CA ASER A 42 -7.791 -4.467 33.410 0.50 40.84 C

If you look at your PDB file you will see that some residues (at least SER 42) has multiple conformations of the side chain.
You will have to select one.

You can remove those (or select the conformation) using our PDB-tools, now available as web server at:

use the pdb_selatloc tool for that.