Fellas, Auctiva has just responded to my ticket and this is what they said:
"I have been informed that activating the eBay/Paypal security key will not cause problems for Auctiva users. This key makes it so a unique number generated by a physical "key" needs to be entered when logging into a customers eBay account. Auctiva never logs into a users eBay account so the new feature does not affect our service."
I'll give it a try and see if I have any hitches. Please feel free to post any problems you fellow Auctiva users experience on this issue. Thanks.