[ubuntu] black screen with blinking cursor on start-up

So, I've been having a bit of an issue lately, and I hope ya'll can help with it. I dual boot windows 7 and ubuntu 13.10 (at least, I'm pretty sure it's 13.10). My windows 7 install is exclusively for gaming. As such I can go months at a time without bothering to coect it to the inteet. Friday night i decided to coect my windows install to the inteet to update my games, get some DLCs and get a new game. while that was going on windows apparently decided to download all the updates I had missed out on over the past nine months or so (I thought I had auto-update tued off, but apparently not). So when I went to shut down the computer I had nearly fifty updates to install - at which point I decided to just let the computer sit oveight and do its thing.

The problems started the next moing, when I booted the computer back up. First up, I immediately noticed the screen seemed a bit dimmer than it should have been, both the starting screen and the grub menu. I ignored it, and tried to bring up ubuntu. At which point I got a black screen with a blinking underscore in the upper left coer. I let it sit for about five minutes before shutting it down and trying again - same result. So I booted up windows, let it configure the updates, then restarted to try again. This time the start screen and the grub menu were back to the proper level of brightness. Unfortunately I still got the black screen with cursor when I tried to load Ubuntu. So I restarted and tried to get in using recovery mode, but that just gave me a wall of scrolling text that ended up getting stuck - both times I tried it (got stuck in the same place both times, but I didn't write down what it said). So, next I tried to boot Ubuntu normally, then just let it sit, hoping it would get past the black screen spontaneously. No joy. I did notice that after about ten minutes the blinking cursor would go away, and I'd have to press a key to get it back.

So far I've only really done one thing to try and fix this. I assumed this was a boot error of some sort and tried using the tool described here - https://help.ubuntu.com/community/Boot-Repair . I used UNetbootin to put it on a jump drive. Then I restarted my computer and told my bios to boot from the jump drive. Unfortunately it didn't work - I got a black screen that said either "boot failed" or "boot failure" or "boot fail" - can't remember which. So I wasn't able to run the boot repair too. My next plan is going to be making a ubuntu boot drive (thumb drive) and seeing if that will boot. If it does I'll at least be able to access my files.

And that's pretty much all I've got. Has anyone else had a similar problem? I'd very much appreciate any advice on how to fix this. Ubuntu is my daily use OS and I kinda need it working, especially with finals coming up.

thanks

edit 4/18 5:45: So, the ubuntu thumb drive didn't work. I made it the same way I made the boot repair drive (using UNetbootin) but I got the same error - "boot fail". I'm going to try it on a different computer in a few hours to check and see if its a problem with the thumb drive or not.