zenika,
Sorry that you are facing this problem.
> Can you please clarify whether you have followed the same steps mentioned here to configure your projects and server with JRebel in MyEclipse ?
> Can you please mention on which application server you have configured JRebel ? Did you add any extra configuration or arguments other than the ones that are specified in the above link ? Is yes, please mention the changes you made ?
> Are there any errors logged in the error log located at <Workspace dir>/.metadata/.log file ? If yes, please attach the .log file to help us investigate further.
> Can you please share your MyEclipse installation details from MyEclipse > Installation summary > Installation details ?
> Can you please mention the steps you followed to install the JRebel plugin in MyEclipse ?