You may try to delete a registry key, or you can run DISE with the "-deletepref" argument. Alternatively, you can begin (un)installing DISE, then tick "Delete preferences" to delete user preferences.
This is the registry key to delete:
HKEY_CURRENT_USER\Software\Steffen L\Dead Island Save Editor\Update\ProgressFile
You can also use the manual download link in case updating fails.
Update
Try to make note of whether your Windows account name has non-ASCI/Unicode characters in it. While I'm not sure, chances are that those characters are not handled properly. For example this may be the case if the text contains Russian characters. To attempt solve this, try to install DISE to a different location.