As you can see here there are such problems with some proxies:
http://support.microsoft.com/?scid=kb%3 ... 62&x=2&y=8
As I don't know yours, and even knowing I don't know its internals I won't be able to help. You want 0 problems, get rid of the proxy. As you won't be able... live with it.
As always, if you want help, then help us with information.
414: URi too long [NoBug]
Moderator: AniDB