ThreadPool.QueueUserWorkItem delegate never gets called

I am using MonoTouch 4.03. I have some code like this:

ThreadPool.QueueUserWorkItem (delegate
{
     Debug.WriteLine("Making connect request");
     client.Connect();
});

About one in 10 times it doesn't get fired. I'm only making very light use of ThreadPool.

NOTE (added 19th July): Currently I have turned LLVM optimisation off and th开发者_StackOverflow社区at appears to have cured it.

This is fixed in MonoTouch 4.06 (or possibly the version before - in any case, it's fixed). I suspect the LLVM optimiser. The MonoTouch release notes show a number of bug fixes in that area.