No offense but i find that hard to believe, but the only thing you can really do is verify you don't have caps lock on and are putting in the right password. There are other known ways, but it is well known that at tomshardware that the people will not assist you with password resets, as there is no way to validate you are the true owner of the device.
I also find it hard to believe a computer would go to sleep then not accept your password, you could do as the person above me stated, the only thing to make it possible is, I believe win 7 has the option to set your password to be changed every so many days, not sure if it's set as default or not, but that's the only way besides the obvious way for the computer to not accept your password.
Only advice I'd offer is bring it to a computer tech shop. I don't know if they check to see if you own the computer or not though.
1. Make sure that the mouse is plugged in correctly and all the way. Pull it out and put it back in
2. Make sure that caps lock is off
If the above fails, restart the computer with caps locks off.
tip - Press back space a couple of times before you start typing, removes any unwanted characters.
as said above, no other way to help you
also on the note of passwords, why can't Microsoft just create a sync profile similar to google but instead the OS registers your PC online. You can have more than one pc to one account and pc's are automatically updated on hardware change. This means that you could just go to your online account with the PC in question linked to it and get a verification code to be entered at the start screen. just a thought. . .