Intermittent 400 Bad Request Errors in IIS

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

Notification EXECUTE_REQUEST_HANDLER

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

Any ideas?

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