this error means that the data source has changed or is not available.
verify that your data source is still working in the Spotfire desktop client. check that the data source is either a linked DB table of some kind and that the information link still works. otherwise ensure any file-based data is embedded in the document.
the error seen on webplayer is pretty high level; it's basically "oh no, something's wrong!" and not very descriptive. if you can share some more including your Spotfire version and relevant logs (don't forget to remove sensitive data) I can probably give you a better answer.