Custom Error Pages

[Rhys666]

OK, an issue I've come across before, but never found a cause for or
resolution of, has decided to become the bane of my life again with ASP.Net
Custom Error Pages.

Basically, my web application is configured to utilise a custom errors page,
in that unhandled exceptions get passed through and the page redirects
correctly as per the settings in the web.config file and Global.asax. This
works in 95% or so of cases, however...

On occasion, and not in any way I see to be replicable, the custom error
handling in ASP.Net/IIS falls over and simply ouputs a standardised error
page stating;
Runtime Error
Description An Application error occured on the server. The current custome
error settings for this application prevent the details of this application
error from being viewed remotely (for security reasons). It could however be
viewed by browsers running on the local server machine.
Details To enable the details of this specific error message to be viewable
on remote machines please create a tag within a "web.config " configuration
file located in the root directory of the current application. The tag should
then have its "mode" attribute set to "Off".
Notes The current error page you are seeing can be replaced by a custome
error page by modifying the "defaultRedirec t" attribute of the applications
configuration tag to point to a custom error page URL.

Does anyone have any idea's of the cause of this, solutions to it, or
workarounds? Even suggestions would do at this point. As I said the
application handles pretty much all errors gracefully, redirecting as
appropriate and outputting the error details, but that 5% or so of cases
where it doesn't is just baffling.
I've tried having everything configured for custom error pages in
Web.Config, in the Application_Err or event of the Global.asax and with a
mixture of the two. I can get all three methodologies working in 95% or so of
cases, but always I return with this issue that on occassion an application
error results in that standard error page with the details supplied above.
It's almost as if the application itself, or the web.config file of the
application, becomes temporarily unavailable.

I really would just like to know why this is occuring at this point.

Rhys

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