That's pretty unfortunate banksta, especially right in the middle of a comp and after all the hard work it sounds like you put into it.
I haven't hardly done much with textures so I don't know much about texture problems, but have you double checked that the texture files you used haven't been moved or renamed.
Also, click on an object that has a missing texture and in the attribute editor see if the file location is still there and if so, try reloading it. I think there's a button near the file path that allows you to do that. Make sure the path an the actual location of the texture file are the same. If so, then at least you've eliminated these as possible causes.
I hope you get it fixed. Maybe it's just a freak thing and rebooting your computer will fix it. Sorry, I can't be of more help.
Don't be satisfied with what you can do but rather strive to do the things you can't do!