Snow Leopard - Cannot Login HELP !

Hi there, hope this post is in the right spot. I have a MBP mid 2009 and Snow Leopard. I have just log out from my wife's account and, when redirected to the login page (I have two accounts registered in the system) I click (using the computer's pad) over my name and picture and nothing happens. Same when I try to access my wife's account. The click just seem to have no effect, and even the text box where you are supposed to fill in the password does not appear. Any suggestions on that ? I cannot access my computer. Please help !

Thanks in advance,
LBM

Reboot from your install disc, launch Disk Utility from the menu, and verify/repair permissions to see if that fixes it. Also check the other tips in this support page from Apple:
Resolve startup issues and perform disk maintenance with Disk Utility and fsck