Un-Ticked Link Phenomenon

I use the links widget in my side bar on a couple of sites, as you know that simply involves setting up the links and selecting the opening style, then saving.

I’m having an issue where the links become un-ticked, in other words I go to my site and there are no links at all listed. I have to go and tick (select) them all again and save. I’m using version 3.6, but this has happened periodically over several versions, and it is a phenomenon that occurs on not just one theme or blog, but on a couple.

I don’t know what would cause this, has anyone else experienced this?

Thank you for your help,