Here is the story
on line 209 of file /wp-includes/theme.php in your account
it's trying to open a directory and read files
but for whatever reason the directory is not being opened.
someone told me they thought it had to do with php so you know what this would mean.
My host changed servers, all of a sudden my files( themes really) can't be read or at least not all of them. They tell me it is not them but i had someone with a fair amount of knowledge looking around in there and this is what he found. He said that he thinks it has to do with php5 but isn't sure.