"Could not load model from ..." But it was working a second ago!

This is a strange problem that I have yet to track down. It appears to be a bug in Eclipse's caching of classpath data. One instant everything is working fine, but suddenly (and forever after), the classpath gets corrupted and the runtime will be unable to find your model even though it is on the classpath. Through some digging, a temporary fix is available.

1. Quit Eclipse
2. go to ${workspace}/.metadata/.plugins/
3. delete org.eclipse.pde.core
4. Restart will take a little longer, but all should be good.

Actually, this will result in the loss of your Target Platform, but that can be fixed here.

If this problem still persists, it suggests that there is a lower level dependency resolution failure of an option dependency. These are not normally reported because they are at a lower level. Check ${userHome}/.jactr/configuration/${projectName}/${runConfiguration}-actual/${timestamp}.log for any errors.