I disabled all auto-action and set email+password as usually but no change. I looked also if some possible Joomla plugin can conflict but it seem to be not the case and the site do not have lot addon installed.
Is not a big deal but I don't like this kind of situation because it seem clear something make conflict somewhere.
Now I don't know... Can you confirm a fresh Joomla 2.5.8 install with last CB 1.9 and Cbsubs 2.0.2 do not have this problem? Due to the fact is a Joomla string who is used, maybe one of the last Joomla update is responsible of this ?
I use Joomla 3.3.6 - CB 2.0.4 - CBSubs 4 - Several Incubator plugins