Lock issue in 406 while re-indexing the site

Hi

I'm having a critical problem with a web site having a pretty large 
number of attached documents (PDF).

After an upgrade from 4.0.4 to 4.0.6_01, I noticed that the search 
returned only a very little number of documents.

First, how can this happen ?

I went for a full site re-index, and for a while it seemed to go fine, 
the site being online and indexing taking place at the same time.

And after a few hours of indexing, we got an error page on the home page 
saying 'the site is lock to anybody but the super admin'.
See below

21807994 [Ajp13Processor[8009][57]] DEBUG - 
--------------------------------------------- NEW GET REQUEST ---
21807994 [Ajp13Processor[8009][57]] DEBUG - New request, 
URL=[/automotive-supplier/Jahia/], query=[null] serverName=[www.valeo.com]
21807995 [Ajp13Processor[8009][57]] DEBUG - Character encoding set as: UTF-8
21807995 [Ajp13Processor[8009][57]] DEBUG - No cookies found.
21807995 [Ajp13Processor[8009][57]] DEBUG - Session is null
21807995 [Ajp13Processor[8009][57]] DEBUG - Session 
BE244AE771768E83221E562A47A219F9 was just created...
21807995 [Ajp13Processor[8009][57]] DEBUG - New session 
id=[BE244AE771768E83221E562A47A219F9]
21807995 [Ajp13Processor[8009][57]] DEBUG - *Jahia is locked by the 
super admin !*

Is this normal ?

What can be done to avoid this but recover/rebuild the search indexes ?

In such situations, what can be done to cancel the indexing process and 
get the site back online ?

(it looks that this have been mostly redone in 4.1 but we prefered to 
deploy a minor release to minimize the compatibiliy issues)

Thanks for your explanations and advices

Regards

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fn:Olivier Vit
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title:Chef de projet technique
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version:2.1
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