New Page Error

Hi,

Tried to add a new page and ended up with this error:
‘Warning: stripos() [function.stripos]: needle is not a string or an integer in ‘…………./cms/wp-includes/functions.php on line 658’
I cannot save the page either.

Could you please help me to solve the problem?
Many thanks in advance.

Cheers,
gannet2

http://wordpress.org/extend/themes/coraline/