Sadly, the latest Vegas and the latest driver for Logitech mice do not get along. Whenever Vegas is the active window, the extra buttons that MouseWare controls does not work and mouse acceleration is disabled.
I have seen this behaviour with another new program, Connectix Virtual PC 5.1. Could it be a common functionlibrary or something that is at fault? Vegas 4 beta was fine.
The latest MouseWare is 9.75. The previous version, 9.73 seems fine.