Help please with randomn blank pages

[demiurgia]

Thanks for that stevesh unfortunately no luck. I tried the debug utlilty and there were no errors. Also tried the errors on screen and no luck. I have looked at lots in the past couple months but still have the problem.
Would anyone have any ideas or possibly at least a guess at which files I might need to check for errors?
My site is here. I am only having the issue on a couple of pages. HERE is link to one of them so you can see what happens. If you go to page 2 here all is ok but click on next or page 3 and you will see there is no listings. It is making it impossible to see some of my products.
Thank you to anyone who has the time to help.