Can't get past the boot screen

[stradastra]

First time poster here...let's see if you guys are as good as I hope!

I'm running Ubuntu on my desktop. I have a dual-boot option between Ubuntu and Windows Vista. When I woke up this morning, my Ubuntu screen was frozen so I attempted to reboot...but I couldn't get past the boot screen. I can get into Windows just fine, but selecting Ubuntu just keeps cycling me through the initial boot screens over and over.

I am a still a beginner so please talk to me as though I were a child. Otherwise I'm sure I'll be confused.

HELP.

[leef]

Are there any error messages or any text at all when you try to boot ubuntu?

[stradastra]

There is no error message. I turn the computer on, it goes to bios screen, then I get the normal "please select which operating system you would like to boot" screen. If I choose Ubuntu, the screen briefly goes blank then returns to the bios screen.

[stradastra]

Can anyone help? Without access to Ubuntu, I have lost literally all of my files, settings, and favorites.