That sounds odd to me.
Can you get a screenshot of the message you receive?
You should never get slow downloads unless we've missed uploading a file to the redirect server. The symptom of that is that the download goes very slowly and to more than 100%
The only other time that could happen is where the DNS is messed up and your machine can't resolve the address of the redirect server and falls back to trying to load from the game server. Again, downloads will go more than 100%
The redirect is hosted on its own VPS on a different physical machine to the game server, with significantly fast connectivity so if you connect to it it should be as fast as your connection can cope with.
Mia_Net is a mutator that sets the netspeed for connecting clients to a higher value than is normal - this is needed to allow the server to send enough data to provide a better flow of information given the high player numbers. The only way I can think you'd get a problem with it is if you've installed an old version of it to your system directory from cache.
Yeah. Need to see the error message to understand what the issue is.