I have a need to upload large files 500MB to 1GB.  When I try to upload anything larger than about 150 MB the upload just stops at 150MB.  No error, no event it just hangs. If I try the same file it will hang at the same point, so I seem to be running into some limit.  I am able to upload 100MB files but I seem to run into a limit around 150MB.  I have increased maxRequestLength in web.config as shown. Any thoughts on what is happening or how I can get to the root of the problem?  Thanks

 <httpRuntime maxRequestLength="2097151" />

We can't tell for sure what the upper limit is. It depends on your environment, what browser you're using and how much free memory you have.
 
The current version of Silverlight buffers the data to upload completely into memory before sending it to the server. It's extremely frustrating. We're trying to find a way to bypass that design limitation and perform true streaming in future versions.
 
In your case, it seems 150MB is the limit. Changing the request size limit on your server won't have any effect since the data never actually reaches the server, the failure point is at the local (client) level.
 
We will work on improving failure detection so that you're at least given an exception when Silverlight stops accepting data.