I had the same problem at my Dell Vostro 1500 with NVidia GeForce 8400M GS with both nvidia-current driver and latest driver from NVidia official site. The problem was solved for me using nvidia-current driver by disabling PXE-boot ability for LAN at BIOS. If somebody has Wake-on-LAN (WOL) setting (Dell Vostro 1500 doesn't) - try to disable both PXE and WOL. Hope this will be helpful for somebody.
I had the same problem at my Dell Vostro 1500 with NVidia GeForce 8400M GS with both nvidia-current driver and latest driver from NVidia official site. The problem was solved for me using nvidia-current driver by disabling PXE-boot ability for LAN at BIOS. If somebody has Wake-on-LAN (WOL) setting (Dell Vostro 1500 doesn't) - try to disable both PXE and WOL. Hope this will be helpful for somebody.