I was playing Oblivion just fine, then the screen went black and I was forced to reboot, when I got back on and tried to run the mod manager it gives me this message;

One or more of oblivion mod managers directories do not exist and cannot be created
Error: Path cannot be the empty string or all whitespace

Push OK and it just closes and does nothing.

It sounds like you may have corrupted files. First try the error checking function in the drive properties - tools. If it can't recover it, you will probably have to reinstall OBMM.