I can't upload files bigger than 20 Mb neither to database nor to disk while the Media.MaxSizeInDatabase setting is bigger than the size of the file. I don't get any messages, just an exception is in the log file.
The value of the maxRequestLength parameter should be bigger than the size of the uploaded file:
<httpRuntime maxRequestLength="1638400" executionTimeout="600" />
This value must be less than the ASP.NET httpRuntime.maxRequestLength setting.