As I wroted on the other ... ignored...thread... I' was having problems with my router.
Well. my findings are...
After updating firmware to the almost imposssible to find 1.11eu b02, and leaving the router almost at its default settings, it's been working flwlessly for a whole week.
Today, I changed language to Spanish. Just after doing that, I checked the logs. Result : WAN connection lost again.
So, this seems to be a bug.
Any comments ?