I need help with this error message…Please Help!

Hi, I receive the following message whenever I try to include gallery related material in a post:

Warning: Compilation failed: characters with values > 255 are not yet supported in classes at offset 16 in /home/webadmin/thomaskayenudes.com/html/wp-includes/shortcodes.php on line 213

Please note that picture filenames do NOT contain any special characters.

Can you help me? Thank you!