The new Android plugin for Eclipse is now available (v8.0.1), and it fixes many bugs, and also became compatible with Eclipse Helios.
More informations here: ADT Plugin for Eclipse
A good review about the the updated plugin can be found here.
Eclipse ADT plugin is not compatible with Eclipse Helios (3.6) as stated on download site. They promise, that this bug will be fixed in the near future, however in the meanwhile you should get Eclipse Galileo (3.5) to use the plugin seamlessly.
Issue fixed, check plugin site!.