We recently upgraded our infrastructure to Windows server 2008 R2 (64 bit), and are now getting intermittent 400 errors on post.

I set up failed request tracing, and have caught a couple of them.

Here are the error details:

ModuleName IsapiModule

Notification 128

HttpStatus 400

HttpReason Bad Request

HttpSubStatus 0

ErrorCode 2147943395


ErrorCode The I/O operation has been aborted because of either a thread exit or an application request. (0x800703e3)

Any ideas?

  • Which ISAPI was running on that request?
    – TristanK
    Jan 24, 2012 at 1:36
  • I'm not sure how to tell that - it just says ModuleName: IsapiModule. How would i look that up? Jan 24, 2012 at 20:38
  • What application framework is the application running? ASP/ASP.Net/other. You're using Failed Request Tracing, so it'll show you the module that's running in ISAPIModule, or at worst you can look at the original request extension.
    – TristanK
    Jan 24, 2012 at 21:13

1 Answer 1


It looks like the answer was a bug in our Kemp load balancers. So far we've had nothing but problems with them.

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