We seem to have the same issue. We checked the KB and we didn't detect anything wrong on the network.
The thing is that is it automatically called every hour through WSI and until someone notices that, the site is down. We can confirm that it apears to be a random thing because we couln't reproduce this behavior.
Might it be that when a lot of customers are making requests on the site while reset cache is kicked off, it might cause this?
PS: sorry for a ressurection of an old thread, but the answer doesn't fix it