Can't delete folder named __MACOSX
I can think of a couple of things.
First, try deleting everything in your .Trash folder with sudo privileges:
sudo rm -rf ~/.Trash/*

If that fails, then try resetting the PRAM on your Mac. Sometimes doing so can surprisingly fix odd errors.
Finally, make sure that the permissions on your .Trash folder are correct
ls -ale ~/.Trash/

The permission for the folder should be like the following:

drwx------  24 username  staff         816 Mar 24 22:06 .
drwxr-xr-x+ 34 username  staff        1156 Mar 24 09:51 ..