Unable to upload big files when running SharePoint on Windows 2008
I had that problem for quite a long time. Changing the maximum allowable file size in SharePoint, or web.config doesn't help. I will just keep hitting a 404 error. Very frustrating indeed.
It was until recently, I found this KB, http://support.microsoft.com/kb/944981/en-us. It states that you will not be able to upload files bigger than 28mb, unless you add the following into the web.config, which will allow you to upload 50mb file into SharePoint, the default configuration.
<system.webServer>
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="52428800"/>
</requestFiltering>
</security>
</system.webServer>
Add this after the configSections, and change the maxAllowedContentLength to [YourMaxFileSize] * 1024 * 1024, and you are done!