I have recently upgraded from Ubuntu 11.04 to 11.10 via the Upgrade Manager. The process went smoothly until the point it came to "Restarting system". At this point the terminal came up with some commands and hex codes. The last command was something with "restart" and nothing happened after that. I had to wait for 5 mins and then I restarted my computer. Since then every time I load linux I get a blank screen. Any help would be greatly appreciated.

I am using a ThinkPad E420 with dual boot - Win7 & Unbuntu (64 bit). I tried booting via the ISO image for 11.10 through a USB stick but then it says "BOOTMGR is missing, press ctrl+alt+del to restart".