Strange graphics problem

I have been using a Ubuntu 12.04/Windows 7 dual boot (not Wubi) for some time now. Recently, I installed the same thing on my not so tech savvy mom's computer because I thought it might speed it up. It has worked very well in that respect, but she is having a strange problem with her graphics, where parts of programs (and particularly webpages) do not scroll or change correctly. For example when scrolling down a webpage, parts of the page will stay where they were before, while others will move. At first I thought this was a lack of memory, so I tried increasing swappiness. When that didn't work, I decreased swappiness, also with no success (or change), and yes, I did edit the actual configuration file, so it retains the changes after reboot. Then I decided this must be a graphics problem, since she is not using any proprietary drivers (as seen in "Additional Drivers"). Therefore I downloaded and installed the AMD Catalyst Driver for Linux (she has an AMD graphics card). However, after rebooting the computer said the graphics aren't working, so I went into safe mode and uninstalled the proprietary driver. After rebooting again, everything worked fine. There is still the page-lagging problem, and I cannot find any other drivers that might work.
My mom has been very happy with Ubuntu overall, and how much faster it is in Windows, but this is a major problem. Does anyone have any ideas?