I was able to get my site back up by modifying the web.config and re-saving it. Does anyone have a clue with what is going on? It's getting very difficult to explain to my clients. Should I upgrade to 4.6.0 as a last resort?

We're having the same problem, with a high load, high visibility site. What we do is check the event log, check for event_id 1309, and then recylce the associated app pool automatically. We use a tool called Hostmon to do this. However, this is hardly a fundamental solution. Do any of you still have this problem with 4.6?

René

This happens to me about once every few weeks, but only on one of my many DNN installations.  The versions range from 3.x to 4.3.5.  However, this only happens on a single v4.3.5 installation.  I have a handful of other sites running that same version.  Right now, upgrading is not an option.  I just need to know how to patch the problem until we can plan to upgrade.  The only thing that fixes this is to clear the cache (by any of the previously mentioned methods), so it seems that the cache is somehow getting corrupted.

*EDIT* By the way, the site that this is happening on also happens to be my most popular site.  It has nothing near the volume of visitors that DNN has so far, but it gets quite a few.  ;)