Fatal error in WPMU THEME

The same problem once occured when I use buddypress theme.

In the edit post, it shows

Fatal error: Only variables can be passed by reference in /home/outlo2/public_html/homeblog/wp-content/themes/wpmu-triden/functions.php on line 26

WPMU-triden 2.1

WPMU-dixi

WPMU-NELO

the same problems.

I am using the newest WPMU

thanks.