Many thanks for that... after waiting for a response via this forum for some time, I eventually did submit a support ticket regarding this issue and quite frankly was disappointed with the end response that suggested it was normal to have this number/level of 404 errors, that they were acceptable and the extension could not be responsible.
They did suggest that I purchase their SEO services to resolve the now nearly 30,000 errors one by one.
Quite a lot of time has passed since that .. a matter of weeks and I only really responded today as someone was kind enough to tray and help.
I have managed to reduce the overall 404 errors and it is WIP and since I have never had this problem on any other website - only this one with a paid subscription to ARTIO SEF. Disappointed.

Thanks for your reply but no it is a Joomla site. I only have this problem on sites where I have Artio SEF installed.

Can someone possibly explain why I am getting thousands of 404 errors... have I set something up wrong, do I have a virus... how do I fix it. Thanks
See folder below.. I cleared it today and within minutes I have over 40 new ones