I'd try re-booting the machine.
What do you mean by this?
"since it stopped giving me access"
& seems different from not being able to quit.
Descrbe what happens when you boot the machine.
You may want to run these "standard" fixes if the problem persists.
1) Check the amount of free space on your harddrive. You should have a several gigs free.
2) You should run disk utility
Macintosh-HD -> Applications -> Utilities -> Disk Utility
a) verify the disk
b) update your permissions.
3) Try a safe boot.
Shutdown your machine. Hold down the shift key. Poweron. Wait awhile; wait awhile while you harddrive
is being checked.
4) Another way to correct filesystem problems is into single use mode.
This page will tell you how to get into single user mode.
Basically, you hold down the command + s key then powering on your machine. The command key
has a little apple symbol on the lower left. It is between the alt/option key and the space bar.
4) You may want to run applejack to clean up your machine.
6) Run hardware diagnostics. It's good for a sanity check.