I presume that, when you've finished a session, you are closing the lid and letting the laptop suspend to RAM. This might be a pain but you could try doing a full shutdown before closing the lid. When you open it, of course, you restart fresh. Try this for a time and see if it still freezes at the login screen. My guess is that it won't.
I could ask how long you wait until trying to login and if you notice the HD activity light to be flashing on and off. If so, this could just mean it's not ready to input from the keyboard. My personal experience with using the hibernate/suspend to RAM shutdown method is that it causes problem. Maybe not right away, but eventually.
I've had this laptop a little over a year and have had this problem off and on but now more frequently: When I open the cover the password prompt screen appears but is unresponsive (frozen) and I have to open and close the cover again (and sometimes again) to get the screen to respond to keying in my password.
While a bit of an inconvenience, I've just put up with it. However, it is occuring more and more often and I'm worried that soon it won't respond at all...
Any suggestions? I'm can't find anything on Toshiba's website that specifically addresses this problem and I'm reluctant to start downloading "fixes" that may only get me in deeper hot water!