Thanks Kevin and Hi Ken (I am from the same side of the Pond as you - welcome on board!) - just a few more from the same location below.
One of the quirks of RW seems to be that different setups, even with all of the required assets installed, sometimes react differently to routes. As an example, I have tried to install, and get running, TDWolf's P&LE (See the RW Thread in Trainsim). I have tried with 3 different incarnations of the route, with all required assets installed (checked through RW Tools) but each time it crashes on me with the "Something bad has happened" message.
This is the only route that this has happened with that I can recall, but others seem to have endless problems.
I am very strict about my downlaods and addition of assets - If I don't need them, I don't install them. I even have mini instalations (not as user friendly as in MSTS - ho hum!) to isolate assets. Takes time, but apart from one major baddie, when I had to reinstall RW from scratch, all has been well so far. A lot of problems run down to assets being installed into different folders, and especially free roam scenarios (or any scenarios) that have stock in them that the end user hasn't got (RW Tools from Mike Simpson is an absolute must for running RW - can check each scenario out before trying to run it).
MSTS was quirky, and, surprise surprise, so is RW

- just need to work at them to get used to the quirks! I am just about, after a year or so of RS then RW. Been a bit of a painful journey at times, but you get there in the end (seem to remember MSTS was the same

)
Rod

