That is godaddy’s customization of the 500 Internal Server Error message. it’s pretty much guarantee that they automatically killed the import process before it was finished, because they deemed it a “runaway task”, i.e. – it had consumed too much server processor (CPU) time.
Two approaches are possible that can help you in this matter.
1. talk to godaddy support, tell them the exact time and date, and what time zone you are in, and ask if they could exempt you from automatic “kill” just until you get the import completed.
2. learn enough about XML to divide up your import file into several smaller files, each less than 200 posts. And do several separate Imports.