I get daily emails from people asking about 430 errors. 430 is a message from the server saying "I don't have a part of the
file".
430 means:
1 - The file is too old and has been deleted during regular cleanup.
2 - The file is too new and it's not on your server yet. This is for
files under 1 day old when you use search or NZB files.
3 - The file has been removed from the server by the server operators.
US based servers have to comply with the DMCA law which means the
servers have to remove copyrighted content at the request of the
copyright owners. This is the most common issue these days.
There are several other potential causes but, most of them are pretty
rare. Some people use non-US servers as backup because they tend not
to implement #3.