The message that says you don't have enough memory means that your computer doesn't have enough memory. The only real true fix is to use a computer which has BOTH a 64 bit operating system and 8GB or more of memory. A workaround is to make sure there are no other programs opened and to export in small batches.
If you can't see the overlay for graduated filter or radial filter, press H
many thanks for your reply. bad news on the memory front! so annoying as I have to close and then open lightroom every time I want to export just 1 photo. As for the graduated and radial filter pressing H toggles between always show and never which allows me to see the circle or lines but it will not show the overlay in red which works for the adjustment brush. The tick box is not there either for the radial filter or graduated filter below the loupe view that is there for the adjustment brush. weird.
The overlay in red is toggled on and off by the letter O