Warning: include(./includes/unicode.entities.inc) [function.include]: failed to open stream: No such file or directory in F:\dropbox\drupal\includes\unicode.inc on line 339

Warning: include() [function.include]: Failed opening './includes/unicode.entities.inc' for inclusion (include_path='.;C:\php5\pear') in F:\dropbox\drupal\includes\unicode.inc on line 339

自己捣鼓，居然出现这个错误。
google了，居然发现很多人有这个问题。
一个解决方案是禁用devel模块。禁用之后，问题解决。