As segwit is active on testnet, blocks will only be downloaded from NODE_WITNESS peers. Though, exactly those peers are disconnected after `BLOCK_STALLING_TIMEOUT = 2` seconds. I am running master (6e6ab2c)

This behavior is consistent across restarts. Sample [debug.log](http://pastebin.ubuntu.com/23058327/) and [getchaintips](http://pastebin.ubuntu.com/23058325/).

It is possible that I shot my own foot at some point, but it seemed smelly enough to create an issue.

{
    strMiscWarning = strMessage;
    LogPrintf("*** %s\n", strMessage);
    uiInterface.ThreadSafeMessageBox(
        userMessage.empty() ? _("Error: A fatal internal error occurred, see debug.log for details") : userMessage,
        "", CClientUIInterface::MSG_ERROR);
    StartShutdown();
    return false;
}
bool AbortNode(CValidationState& state, const std::string& strMessage, const std::string& userMessage="")
{
    AbortNode(strMessage, userMessage);
    return state.Error(strMessage);
}
} 
/**
 * Apply the undo operation of a CTxInUndo to the given chain state.
 * @param undo The undo object.
 * @param view The coins view to which to apply the changes.
 * @param out The out point that corresponds to the tx input.
 * @return True on success.
 */
static bool ApplyTxInUndo(const CTxInUndo& undo, CCoinsViewCache& view, const COutPoint& out)