I'm getting a lot of these error messages in my logs on one of my servers and intermittently on two others.
Googling didn't reveal very much information, mostly related to file uploads or downloads being interrupted.
My pages are basically just text files with "ok" in them that only have .aspx extension for future plans, there's no actual code powering the pages. Servers are all Windows Server 2008 RC2 x64 running IIS7 / ASP.NET 4.
Statistically it's happening well under 1% of the time but because of the volume of traffic that still clutters my event log with 2 or 3 of these messages per minute.
Edit: I tracked down the problem, setting buffering to true stopped it occurring.