A late follow-up, in case somebody may find the information some day.
I gave up on understanding the problem at this point, however, later on, I moved to a dedi. And, this time, no more version check problem.
Previous bugged configuration : OVH Premium web hosting with included SqlPrivé database handling. New working configuration : Kimsufi 16G with Debian Squeeze.
So, case solved, even if the reason behind the problem will forever remain a mystery
