Original issue: BUG-134040
Reproduction steps:
You have a working SOCKS5 proxy which is prepared to proxy Second Life traffic.
  1. Attempt to configure a SOCKS5 proxy via
    Preferences -> Setup -> Adjust proxy settings
  2. Attempt to use Second Life
Expected: The viewer is able to proxy UDP traffic through SOCKS5
Actual: Proxy does not work
Note, this problem appears to be from a race condition when performing a handshake between the proxy and viewer. This may succeed on some machines and fail on others.