I once saw the same thing happen due to screwed-up permissions on the .Trash folder. xUKHCx's suggestion should work if no folder exists, but I'm pretty sure the Finder will create it when it launches if it doesn't exist. In my case I think I did it the other way around--I deleted that folder then let Finder recreate it.
So in the event that the folder DOES exist and you're still having trouble, you'd want to use the following command:
If it complains that you don't have permission to delete that, then that's probably the problem. You can then add "sudo " to the begining of that command (so "sudo rm -R ~/.Trash"), at which point you'll get a password prompt and it should delete it no matter what.
Once you've removed the .Trash folder, it should re-create automatically if you either log out and back in, or use the force quit dialogue to re-launch Finder. You could also use "mkdir ~/.Trash/", like xUKHCx suggested, to manually recreate it if it doesn't get created automatically.
In either case, I'd also open Disk Utility and run "Repair Permissions"--it may not help, but if the trash is screwed up something else might be, and it certainly won't hurt anything.