Alejandro,
The issue is not clear to us.
Can you please give us some more information to help investigate further?
1. Is the project created in MyEclipse or is it a WTP enabled project ?
2. Are you seeing this error when trying to deploy a project to a server ? Please list the exact steps you are following along with the server details.
3. Is the issue only with this particular project ? Share details about the project.
4. Can you make sure you have configured the JRE under Window > Preferences > Installed JREs?
5. Clear the contents of the .log which is located at <workspace dir>/.metadata/.log. Replicate the issue and copy paste the contents of the .log file here for us to take a look.
6. Also share the MyEclipse Build ID from Help > About.