thanks for the replies

this only happens in very specific circumstances - when I use UNDO after having used auto-ripple set to 'all tracks, markers, regions' - I have not seen it happen under any other circumstances

none of my other audio applications have this bug and M-audio have said that while their drivers work on SP3 the installer wont allow it to install so I can't re-install the driver - it seems unlikely to me anyway TBH, it's pretty 'bug-like' behaviour because it is so specific and completely consistent to the point where I have to remember to turn off Auto-ripple before using undo - which is difficult as I am in such a habit of using ctrl+Z

cheers