I have a user that will have open 3 or 4 PDF's in Adobe Reader X. When the user starts flipping between the PDF's. the screen starts to go dark and the text disappears on one or more document until it's closed out and reopened. The PDF's are about 300 pages each of text. I did all updates to windows and to adobe and it still happening. The computer is running Windows 7 32bit. It's a Dell 980 with 4GB of RAM. Any advice would help.