A user gave me their Acer Apire One running Linux; it was doing exactly as above (boot up into a completely black screen with mouse pointer, no bars, no frames, no windows, no fun).
Linux is a fiddly OS, and such joy to repair... When the AA1 boots, start hammering CTRL-C until it displays a command prompt rather than the blank screen with pointer. Whatever your problem, this is the first step into fixing it.
Type in su then enter (to switch to the root user).
Enter the password if applicable.
The first thing you can try is starting GNOME. Type in gdm then enter. This should display a login screen. In the username field, try typing in root, then whatever your password is for the root user. This should give you an interface of sorts, depending on what the underlying issue is. You can try logging in as another user if you know one. What should happen is that a message will appear informing you that the session closed within 10 seconds, then kick you back out to the command line.
The next thing to try is making sure that permissions are correct. Try typing in the following:
chown -R user:user /home/user
Substitute user for your particular username. If you have the same problem as I did, you will get lots of input/output errors next to a few files.
Lastly, perform a disk repair on the hard disk. In Linux terms, performing a disk check on a mounted drive is a big no-no, but it's worked for me many times (mainly because the systems I've been repairing haven't been "essential" systems, so there's been little risk if it does go FUBAR). This step is up to you; if in doubt, don't do it.
You can try unmounting the hard disk by typing:
Press Y for every option that comes up. Once finished, reboot the laptop and see if that's made a difference. It did for me, and I now have one very relieved user. The main problem with this laptop is that the battery died, so it's very likely that this issue is caused by sudden power outages.
Hope it helps!