There is currently an issue with OVH that caused one database server to stop responding inside the VLAN.
This issue is affecting about 1/3 of the instances hosted.
Details: http://travaux.ovh.net/?do=details&id=38642&PHPSESSID=64dba8ac3b9655040ecac096e4e56434
I'm really sorry about this but hopefully they will fix this soon.
If I get more information I will post it here.