Thanks for everyone's input and support! I've done everything suggested but still having the same problem. I can list one or two (if lucky) auctions but then the site just dies....it's either extremely slow in responding or won't respond at all. All of my computer software is kept up to date and I've done diagnostic checks for internet connectivity. Everything's OK here.
I'm pretty much at the point where I'm ready to go back on ebay for listing my auctions. Sure it costs a bit more and no great templates, but at least I'll get my listings posted and make some sales.
I am kind of curious though how Auctiva can maintain their server network without collecting any fees. I can't use their insurance service because I'm from Canada and their site only supports U.S. shipping. Might this be the reason I'm having problems getting my listings posted?