vw_get_message

there is a problem in vw_get_message. 
You should change line 568 in virtualWire.cpp to
    if (_len != rxlen)
instead of 
    if (_len > rxlen)

Actually if the transmission sends a number of bytes that's less than the number of bytes sent before, there will be no problem. If the number of bytes transmitted raise again, then you will still receive the last lower number of bytes.
