GTX 560 Ti - not enough memory. So now what?

Question

I upgraded my old card to a GTX 560 Ti with 1GB RAM for use with Premiere Pro.  Works great with hardware rendering sometimes (I had to add the card to the CUDA text file to enable acceleration).  But half the time when skimming through a project or rendering, it spits out an error:
"Your hardware configuration does not meet minimum specifications needed to run the application. The application must close."
http://nvidia.custhelp.com/app/answers/detail/a_id/3008
My drivers are all up to date. From what I've gathered, as soon as Premiere Pro eats up more than 1GB memory, the video card conks out and causes a crash. My projects are mainly image based (I rarely use any actual video), with some images being higher than 1080p.
So is the problem the amount of RAM on my GPU?  I've got 8GB in my PC, why can't Premiere use that RAM once the video ram runs out? If I switch back to software rendering it doesn't crash, but of course it takes 4 times longer to render. With my last project, I noted in the Task Manager that Premiere Pro used up 2.2GB of RAM. Does this mean I need to get a GPU with 3GB RAM in order to use acceleration?
thanks for any responses.

Answer 1

Thanks for your replies.
I'm running an i7 2600K, 8GB RAM, Asus P8H67-I Deluxe, Premiere Pro CS 5.5.2. My last project that it crashed on is 1080 25fps, with many of the images being around 4000x2000. It's basically slideshow material with a couple Sapphire effects here and there. I've just gone in and switched off all Sapphire plugins in the project just incase that might be the problem, and went to render the project. Same error.
I get the same error occasionally on other projects. Sometimes it will fully render with no problem, but other times it will conk out fairly quickly. Some projects seems more susceptible to the crash than others, and I have to switch to software mode.
Here's a screenshot of the error:
thanks