Order and user exist but in admin don't appear

Hi all,
I have a weird issue that cannot figure out and I wonder if somebody faced the same thing and solved.
I run a OC 1.5.1.3, all ok, all working smoothly, some QMode extension, some core modify but all working correctly since 2 years and half ago.

Suddenly, in administration panel, the order number, the customers number and all statistics are freezed at the end of april 2013.

The funny story is that in database all data exists: new customers, new orders, alla data updates, the checkout system works well (there is a request quote mod), the user has created, the order too, customers and admin correctly receive email messages, all it's ok but admin update.

I tried to repair/optimize the db, flush all caches, deactivated/reactivated all extensions, no success.
PHP 5.3.x/Apache
Any idea to solve or investigate further is welcome, I finished mine, thanks in advance for your help.

Marco