problem under PHP 5 with APC as opcode cache. See details:
http://mail.wikipedia.org/pipermail/wikitech-l/2006-January/033660.html
* Small changes to tabs in Monobook skin c/o Chris Ware
+* (bug 4679) Work around buggy basename() function in PHP5, which breaks
+ uploads of files starting with multibyte characters on Linux.
+ wfBaseName() doesn't suffer this bug, and understands backslash on
+ both Unix and Windows.
=== Caveats ===