Screen saver freezes computer

I had my PC (Dell XPS 435T, with Win7 Ultimate 62 upgrade from Vista Ultimate 62) set to go into screen saver mode (with my pictures shuffled) after 5 minutes and then upon resumption logon with password to get back to the desktop. I found that the longer the screen saver was on, the longer it took to get back to the desktop. First, there would be a delay at the log-on screen (it would take 3-4 minutes for the desktop to appear), then if I waited for more than 5-6 hrs, the delay would occur when clicking the screen saver (it would freeze for 4-5 minutes), and no delay after I entered the password on the logon screen.

I now shut off the screen saver, and just use the "lock" option when sutting down my computer - and no delays. Could the screen saver photos just slowly jam the memory, or something like that - and is there a solution? I did not have this problem with Vista.

Thanks. I have 12 gb of RAM, which was enoguh when i was using Vista

This is quite frustrating, though a minor problem. I isolated it - it only occurs if screen saver is on. I can lock computer and then go back on, without a problem. The amount of the delay is proportional to the amount of time screen saver is on - longer it's on, longer the delay. And interestingly, the delay first manifests itself in a blue screen after logon from locked screen, and then if I wait longer to click through from the screen saver, the delay is when I click the screen saver (it freezes), and there is no delay on logon.

I can just avoid screen saver, but I enjoy watching all of my photos flashing by (by the way, the problem occurs even with a simple screen saver, like bubbles). Somehow, some cache fills up and needs to be deleted when I click on the screen saver.

Someone suggested a clean install, but I truly don't want to go through all of that - reinstall all of my programs, data, etc.