Don't have a Nvidia card (Mobility Radeon HD 3650 and Radeon 9200 SE), tried the reg key anyway, but to no avail. I'm only having this problem with Qt-4.5 apps. Tested Psi (http://downloads.sourceforge.net/psi/psi-0.12.1-win-setup.exe) which is using Qt-4.4.3 and it's OK. Thanks for the suggestion though.