hook_node_insert() sporadically not being fired after node_save() I have a situation where, every once in a while, I'll save a new node, and hook_node_insert() appears not to be called--AT ALL, for any of the modules that implement it. For example, if I look through recent log messages, there is no watchdog message pertaining to the new node; no "your node has been created" message is displayed to the user; none of my custom modules which implement hook_node_insert() are fired. Yet, the node appears to have been successfully saved: It show up after being saved, shows up in content listings, etc. (Though anything that was supposed to happen via another module's hook_node_insert() call does not happen.)

The maddening thing about this situation is the "sporadically" part: Most of the time everything works as designed, and hook_node_insert() fires, but once in a while it doesn't.(Maybe, once out of ten or twenty times, it doesn't fire.) 

So at this point I'm just looking for any clues or hints as to where I should be looking for the problem.
Is there anything that this kind of strange sporadic behavior might point to?

One thing I've wondered is if this could somehow be related so some kind of cache issue. Specifically, I'm using memcached on my site, which I'm using to hold every cache table from my database. Could there be some kind of issue there? I'm starting to experiment with removing certain tables from the memcached cache (like cache_form), but no leads yet.
The only other note I'd make is to ensure that you don't have an &amp; (ampersand) in front of $node in your function definition.  I was porting from a drupal 6 site's nodeapi function and was using hook_node_insert(&amp;$node) and it wasn't until I removed the ampersand that it started working.