Are You sure then You've got latest drivers? You can get them from Ati site here. Just click there on Motherboard Integrated Video - Full Catalyst Software (or invidual there You may change english language for other) and choose Win7 32 bit. There is now 9.9 version driver.
Before installations of new driver remember to uninstall old one first.
This error usually means then Your motherbaord is overheated. Normally there will be BSOD but Ati software react on that problem by reseting graphic card. Check Your temps with Lavalys Everest or HwMonitor . If temps will be to high use compressed air such as this and clean out all the vents with it. Laptop must be switched off and without battery.
Minimum once per year I always recommend manual clean of heat sink and fan. You may try to do it also if compressed air won't help.
How to do it check Your service documentation if it's avaible on Lenovo site. Do it only on Your own if You can do it and You if don't have warranty on it.
If You still have warranty don't clean it manually on Your own because You will loose it.