I never leave either program running in the 'systray' when not downloading and only use BitTorrent when LW cannot find or download the file as it tends to be slower. No LW opens as normal, suggests I update to LW PRO and after clicking later runs in exactly the same fashion it did when it worked previously.

So, what you're saying is that there are certain files you can download:
" .. and started to download without any problem "
Those checked and confirmed with Bitzi.....right?

And while trying to download with LW, your bittorrent is completely closed (checked via Task Manager>Processes)???

Since LW is asking you to update (to a newer version rather than to Pro), what LW version are you using, and where did you get it from (the official LW website [http://www.limeiwre.com])??
What about your free diskspace you download with LW to??

Recently I have found a lot faked files with even less than 3 hosts; obviously shared by the RIAA to discourage P2P users from downloading copyright protected material........

__________________

"Never Argue With An Idiot. They Will Drag You Down To Their Level, Then Beat You With Experience"