After converting c# Script, Unity is giving errors on multiple lines which were fine before.

When saving in MonoDevelop, I got the message "File has line endings which differ from the policy settings." - And It gave me the options to convert. After I pressed the convert button, the script starded to give me errors on multiple lines, even though the script used to run fine. Why did it give me this "has line endings which differ from the policy settings." -message, and how do I fix the problem?