I replaced Ubuntu 11.10 with 12.04 64 bit beta on my brother's laptop 1 1/2 weeks ago. Everything worked perfectly until last night when I did updates for him. Following the updates, which were listed as a Partial Distribution Upgrade, upon rebooting, there was not any display after entering the password during boot. It is an HP dv6910us laptop with NVidia Geforce 7150M graphics. Unity and this computer worked perfectly with 11.10, and also with 12.04 prior to last night. I've tried two complete fresh installs. The recommended NVidia Driver, which is presently 295.40-0ununtu1 is not installed during the install of 12.04. In checking the NVidia site, this driver was just relesed 4/11/12. I'm guessing that this driver is the issue, and it was updated from whatever the previous recommended driver was during last nights install. NVidia did say earlier on their site today that there were instances of it causing Unity to freeze. If I boot in 2D, the system does funtion. If I install the 295.40 driver when booted in 2D mode, it will not fix the problem and I still can't boot in Unity 3D. Thank you for your help.
Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug 982485, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Feel free to continue to report any other bugs you may find.