HTTP/1.1 New Session Failed

I'm on a windows VPS and I run ASP applications with mysql. I have a
lot of traffic so I know I use a lot of resources... but here is my
problem:
The server is running and after some hours I get this error
message:HTTP/1.1 New Session Failed

I've supposed this is caused by the leak of memory, so I've tried
different thing without any improvement..
- create a paging file
- set the pool recycling when at a "maximum virtual memory" amount
- set the session timout in the webconfig at 5 minutes

Nothing has changed. I don't know if I had some little improvements,
however nothing that prevent the server from displaying that error
after some hours of running properly.