I have modificated Manifest.xml to register a new Acivity... it first writes 'Resource is out of sync' and then simply deletes R.java and R.class (it has disappeared and I cannot load pictures etc.)

why does this happen?? it is not the first time.........

Because you can edit the location of the R.java in the Manifest, so eclipse will make a new one I guess. Normally Eclipse should make a new one. If it doesn't, try refreshing your project tree (in the left) or edit some value in strings.xml this should force Eclipse to build a new R.java

Thanks.

At least, it has created a new R file, but it has lasted a while

This issue is a real weak point of the Android SDK

One little error in the Manifest file, and there is 'Resource is out of sync' for half a day

Google should fix that quickly.................so terrible

*EDIT: Even after having deleted the project and loaded the back-up (which worked fine), the 'resource is out of sync' remains, no matter what I do... so that means the entire project bound to the particular project name is frozen......