This works with AEM 6.3 as well. Unchecking the "Resolve sources..." Fixes the issue as Vaibhav suggested. Thanks

I was facing this error sometimes back when doing "Export to server" from content jcr_root. I am using Eclipse AEM Developer Tools 1.1.0.The way the issue was resolved was to do the vault import once:Go to your content jcr_root folder, and use the vlt command>vlt import -v http://localhost:4502/crx ...