One additional piece of information: this seems to be related to the combination of motherboard and GPU; I tried the same GPU (G260) on another machine, running ubuntu 11.04 and it works just fine. My motherboard is an ASUSTeK M2N-VM HDMI, with a NVIDIA GeForce 7050PV/nForce 630a chipset. (a bit ironic that the Nvidia card refuses to work with a Nvidia motherboard =) )
One additional piece of information: this seems to be related to the combination of motherboard and GPU; I tried the same GPU (G260) on another machine, running ubuntu 11.04 and it works just fine. My motherboard is an ASUSTeK M2N-VM HDMI, with a NVIDIA GeForce 7050PV/nForce 630a chipset. (a bit ironic that the Nvidia card refuses to work with a Nvidia motherboard =) )