We are getting intermittent problems on a production server that we cannot recreate.

There are two very strange things about the issue. Firstly it's a method not found error on the constructor (ctor) for an exception handling helper class and secondly we have custom errors switched on for remote users and this property is being ignored.

The detail of the error is:

> 
> Server Error in '/MyWebsite' Application.
> =========================================
> 
> 
> 
> 
> ---
> 
> 
> 
> 
> Method not found: 'Void MyExceptionHelperClass..ctor (System.Exception)'.
> -------------------------------------------------------------------------
> 
> 
> ...  
> 
>  Exception Details: System.MissingMethodException: Method not found: 'Void MyExceptionHelperClass..ctor (System.Exception)'.  
> 
>  ...
> 
> 
> 

The stack trace is pretty unhelpful. 

My thoughts are that there may be an out-of-memory error or something like that that is killing the page. When the exception handling code kicks in it tries to create an exception object which fails for the same reason giving this error.

However this is wild speculation. We are waiting for the event logs to see whether anything is amiss with the server but in the meantime does anyone have any thoughts or suggestions?

**UPDATE:**

It has proven difficult to get information out of the team responsible for the production servers but I have managed to find out that as far as load balancing is concerned, this site is currently only running on one server (this can be made to switch over onto another if necessary). Given that this is an intermittent problem and there is only one server involved, then I find it difficult to believe that this could be an assembly issue. Surely if it was then the problem would occur every time?